Exam 2 Flashcards
What is amyloidosis
Disease where an abnormal protein (some cases derived from Igs) deposits in tissues
Besides timing, what is the difference between adaptive and innate immunity
Adaptive can respond to other foreign substances besides just microbes
What are the major components of innate immunity
Epithelia (blocks entry), NK cells, dendritic cells, phagocytic cells, complement system
What do epithelial cells do to prevent entry of microbes
Produce antimicrobial molecules (defensins), lymphocytes located in epithelia combat microbes
What do natural killers provide defense against
Viruses and intracellular bacteria
Which complement pathways are used in innate immunity
Alternative and lectin
What other proteins are involved in innate immunity
CRP, mannose-binding lectin, lung surfactant
What recognizes PAMPs and DAMPS
Pattern recognition receptors
What are pattern recognition receptors found
Plasma membrane (extracellular microbes), endosomes (ingested), and cytosolic receptors (intracellular)
Where are TLRs found?
Plasma membrane and endosomes vesicles
What pathway do TLRs activate
NFkB which stimulates the synthesis and secretion of cytokines and expression of adhesion molecules AND interferon regulatory factors, which simtulate the production of antiviral cytokines (type I IFN)
What is NOD-like receptor
Recognizes products of necrotic cells, ion disturbances, and some microbial products; signal via inflammasome; gain of function of this receptor results in periodic fever syndrome (called autoinflammatory syndrome) -> treat with IL-1 antagonists; also involved in gout (recognizes urate crystals), obesity-associ T2DM (detects lipids) , and atherosclerosis (cholesterol crystals)
What are C-type lectin receptors
Expressed on plasma membrane of macrophages and dendritic cells; detect fungal glycans (illicit response to fungi)
What are RIG-like receptors
Located in cytosol, detect nucleus acids of viruses and replicate in cytoplasm of infected cell; stimulate production of antiviral cytokines
What do GPCRs on neutrophils and macrophages do?
Recognize short bacterial peptides containing N-formylmethionyl residues; stimulates chemotactic responses
What do mannose receptors do
Recognize mannose on microbes and induce phagocytosis of microbes
How does the innate immune system provide defense
Inflammation and antiviral defense (type I IFN act on infected and I infected cells and act on enzymes to degrade viral nucleus acid and inhibit viral replication)
What are the types of adaptive immunity
Humoral: against extracellular microbes and their toxins (mediated by B cells and abs)
Cell-mediated: against intracellular microbes (mediated by T cells)
What are effector and memory cells
Lymphocytes that have come into contact with their antigen
What functions do B cells ultimately have on microbes
Neutralization of microbes, phagocytosis, compliment activation
What is clonal selection
Lymphocytes express a receptor specific for an antigen -> antigens will specifically activate the antigen specific cell; all clones express same receptor
How is antigen receptor diversity generated
Somatic recombination of genes that encode for the receptor protein during maturation in the thymus and bone marrow; mediated by RAG-1 and 2 (recombination activating genes) -> inherited defects in RAG causes inability to generate mature lymphocytes
What can be a marker for T and B cell lineage
Presence of recombined TCR or Ig genes; only cells that recombine germline antigen receptor genes
What can be used to detect tumors derived from lymphocytes
Analysis of antigen receptor gene rearrangements (since each T or B cell and clonal progeny have unique DNA rearrangement)
What does the alpha beta TCR recognize
Peptide antigens presented by MHC molecules
What is the TCR linked to
Six polypeptide chains which form CD3 complex and chain dimer (identical in all T cells); involved in transcription of signals into the T cell
What does the gamma delta TCR recognize
Peptides, lipids, nd small molecules without presentation by MHC; tend to aggregate at epithelial surfaces (skin and mucosa of GI/GU tracts); sentinels that protect from microbes trying to enter through epithelia
What are NK-T cells
Recognize glycolipids displayed by MHC-like molecule CD1; function not well defined
What are CD4 and CD8 expressed on
Alpha beta T cells
What do integrins do in the T cell response
Promote attachement of T cells to APCs
What is located on the surface of all mature, naive B cells
IgM and IgD (antigen binding component of B cell receptor complex)
What happens to B cells after stimulation by antigen
Develop into plasma cells (make abs); also in blood called plasmoblasts
What makes up the B cell receptor complex
Heterodimer of Igalpha (CD79a) and beta (CD79b) -> invariant; signal transduction; also contains type 2 complement receptor (CR2/CD21) -> recognizes complement products; CD40 (receives signals from helper T cells); *CR2 used by Epstein Barr virus to enter and infect B cells
Where are dendritic cells located
Under epithelia and interstitia of all tissues
What are langerhans cells
Immature dendritic cells located within the epidermis
What are follicular dendritic cells
Dendritic cells located in germinal centers in the spleen and LN; have Fc receptor for IgG and receptor for C3b; can trap antigen bound to abs or complement; plays a role in humoral response by presenting antigens to B cells and selecting the B cells that have the highest affinity for the antigen
What are the general roles of macrophages in adaptive immunity
Present peptides to T cells, effector cells in cell mediated immunity (t cells activate macrophages to make them better at killing ingested microbes), and effector cells in humoral immunity (destroy opsonized microbes)
What is the function of NK cells
Destroy irreversibly stressed cells (virus infected and tumor); do not express TCRs or Ig, have azurophilic granules; can kill without prior exposure; express CD16 and CD56 (markers); CD16 is a Fc receptor for IgG (can lyse IgG coated targets - called antibody dependent cell-mediated cytotoxicity)
How is the functional activity of NK cells controlled
Activating receptors: NKG2D family -> recognize surface molecules induced by stress Inhibitory receptors: recognize self class I MHC molecules (expressed on all healthy cells)
Which ILs stimulate the proliferation of NK cells
IL 2 and 15
What is the effect of IL-12 on NK cells
Activates killing and secretion of IFN-y
What are innate lymphoid cells
Lack TCRs but produce cytokines similar to that made by Tcells; NK cells are an example; different subsets produce IL-5,17,22 and IFN-y; function as early defense, stress surveilance, and shaping adaptive response. By providing cytokines that influence differentiation of T cells
What are generative lymphoid organs
Where T and B cells mature; also called primary or central
What is the function of the spleen
Blood born antigens are trapped here by dendritic cells and macrophages
What are the cutaneous and mucosal lymphoid systems
Cutaneous: located under epithelia of skin
Mucosal: located in GI and respirator tracts (pharyngeal tonsils and Peyers patches)
Where are B and T cells located in LN
B cells: follicles in the cortex; if recently responsed to an antigen, may have germinal center; contains follicular dendritic cells
T cells: paracortex; contains dendritic cells
Where are T cells and B cells located in the spleen
T cells: perioarteriolar lymphoid sheaths surrounding small arterioles
B cells: follicles
Where are the genes that encode for HLA molecules located
Chromosome 6
Describe the structure of MHC I molecules
Heterodimer of polymorphic alpha (heavy chain) linked to nonpolymorphic protein called beta2 microglobulin; alpha chains encoded by HLA-A,B, and C; extracellular region of alpha chain divided into three domains; alpha1 and 2 form a cleft for peptide binding (AA resides line the sides - explains why different class I alleles bind different peptides)
What do Class I MHC molecules display
Peptides derived from proteins (viral and tumor antigens) located in cytoplasm and produced in the cell
Describe how proteins are displayed by class I MHC
Cytoplasmic proteins degraded in proteasomes and transported to ER where they bind to MHC I molecules; associate with beta2microglobulin that is transported to surface
What does the alpha 3 portion of the class I MHC molecule bind to
CD8
Describe the structure of class II MHC molecules
Heterodimer of alpha and beta chain (both polymorphic); extracellular portion has alpha 1, alpha 2, beta 1, and beta 2; cleft formed by alpha 1 and beta 1 (this portion is where most differ)
What do class II MHC molecules present
Antigens internalized into vesicles, typically derived from extracellular microbes and soluble proteins
Describe how class II molecules present their antigen
Proteins are proteolytically digested in endosomes or lysosomes; peptides associate with class II heterodimers in vesicles and transported to surface
What does the class II beta 2 domain bind to
CD4
Besides MHC genes, what else does the MHC locus encode for
TNF, complement components, lymphotoxin
Which cytokines are released in innate immunity
TNF, IL-1,12,type I IFNs, IFN-y and chemokines
What is the main producer of cytokines in adaptive immune responses
CD4 T cells; IL-2,4,5,17, IFN-y, TGF beta, IL-10
What are colony stimulating factors produced by
Marrow stromal cells, T lymphocytes, macrophages; ex: GM-CSF and IL-7
What can be used to treat rheumatoid arthritis
TNF antagonist
What is the difference between what T cells can recognize versus B cells
T cells just peptides
B cells: proteins, polysaccharides, and lipids
What is an adjuvant
Given with protein antigen in vaccines; activates innate response; activates APCs to express costimulators and secrete cytokines that stimulate proliferation and differentiation of T cells; principal costimulators are B7 proteins (CD80 and 86) on APCs, recognized by CD28 on naive T cells
What is “signal 2”
Triggered by costimulators; ensures that adaptive immune response is only induced by microbes; immune responses to tumors, signal 2 can be DAMPs from necrotic cells
What does CD40 ligand do
Expressed on activated T cells; binds to CD40 on macrophages and B cells and activates them
What do TH2 cells secrete
IL-4 (B cells differentiate into IgE)
IL-5 (recruits eosinophils)
What are T-dependent antibody response
Some ab responses to protein antigens require T cells; B cells ingest protein and present them to T cells via Class II MHC; T cells stimulate B cells
What ab do polysaccharides and lipids cause the release of
IgM
What ab do protein antigens cause the release of
Different classes IgG, IgA, IgE; isotope switching (induced by IFN-y, and IL-4); helper T cells also stimulate production of abs with high affinities for antigens (called affinity maturation)
Where do isotope switching and affinity maturation occur
Germinal centers, which are formed by proliferating B cells
What are follicular helper T cells
Helper T cells that migrate into the germinal centers to stimulate isotype switching and affinity maturation
Which abs opsonize
IgG
Where is IgA secreted
From mucosal epithelia in respiratory and GI tract
What ab is actively transported across the placenta
IgG; protect newborn
What happens to the effector lymphocytes after the microbe has been eliminated
Most die by apoptosis
Which cytokines induce the differentiation of Th1,2,and 17
Th1: IFN-y and IL-12
Th2: IL-4
Th17: TGF beta, IL-6, IL-1, IL-23
What does Th1 cells trigger
Macrophages activation and IgG ab production
What is the Th1 role in diseases
autoimmune and chronic inflammatory diseases (IBD, psoriasis, granulomatous inflammation)
What is the role of Th2 in disease
Allergies
What is the role of Th17 in disease
Autoimmune and chronic inflammatory diseases (IBD, psoriasis, MS)
Which part of the Ig switches in isotype switching
Heavy chain
What are immediate (type I) hypersensitivity reactions
Caused by Th2 cells, IgE abs, mast cells and other leukocytes
What are type II hypersensitivity disorders
Ab mediated; secreted IgG and IgM abs injure cells by promoting their phagocytosis or lysis and injure cells by inducing inflammation; abs can also interfere with cellular function and cause disease without injury
What are type III hypersensitivity reactions
Immune-complex mediated; IgG and IgM abs bind antigens in circulation and deposit on tissues, inducing inflammation; leukocytes are recruited and produce tissue damage by release of lysosomal enzymes and generation of free radicals; causes necrotizing vasculitis (fibrinoid necrosis)
What are type IV hypersensitivity reactions
Cell-mediated immune disorders; sensitized T lymphocytes (Th1,17, and CTLS) cause injury; causes perivascular cellular infiltrates, edema, granuloma ormation
What are the phases of Type I hypersensitivity reaction
Immediate reaction: vasodilation, vascular leakage, and depending on location, smooth m spasm or glandular secretions; subside in a few hours
Late phase reaction: (common in allergic rhinitis and bronchial asthma) sets in 2 to 24 hours later and can last for several days; characterized by infiltration of eosinophils, neutrophils, basophils, monocytes, and CD4 T cells; mucosal epithelial cell damage
What is an example of Type II hypersensitivity reaction
Autoimmune hemolytic anemia, Goodpasture syndrome
What are examples of type III hypersensitivity
Lupus, glomerulonephritis, serum sickness, Arthur’s reaction
What are examples of type IV hypersensitivity
Contact dermatitis, MS, T1DM, TB
What is the role of IL-13 in type I hypersensitivity
Enhances IgE production and acts on epithelial cells to stimulate mucus secretion
Where are mast cells derived from
Bone marrow
Where are mast cells abundantly found
Near BV and nerves and in subepihtlial tissues; explains why local immediate hypersensitivity reactions occurs at these sites
What are some things that induce mast cell secretion
IL-8, codeine, morphine, adenosine, mellitin (bee venom), head, cold, sunlight
How are basophils similar to mast cells
Have Fc IgE receptor and cytoplasmic granules; different because not present in tissues -> circulate blood in small numbers
What happens when an antigen binds to a sensitized mast cell
Antigen binds to and cross links adjacent IgE abs; underlying Fce brough together which activates signal transduction pathways from cytoplasmic portion of receptors
What are the preformed mediators in mast cells
Vasoactive amines (histamine), enzymes (neutral proteases: Chymase and tryptase and acid hydrolases -> cause tissue damage and lead to generation of kinins and complement); proteoglycans: heparin and chondroitin sulfate (package and store amines in granules)
What are the secondary mediators found in mast cells
Lipid mediators (leukotrienes, prostaglandin D2, and PAF): reactions in cell membrane activate phospholipase A2 to produce AA; *PAF not derived from AA -> causes platelet aggregation, release of histamine, bronchospasm, increased permeability, and vasodilation Cytokines: TNF, IL-1, chemokines (leukocyte recruitment -> late phase reaction), IL-4 (amplifies Th2 response)
What is the immediate type I hypersensitivity reaction characterized by
Edema, mucus secretion, smooth m spasm
What is the late phase reaction believed to be involved in
Allergic asthma; treatment requires broad spectrum of anti inflammatory drugs such as steroids instead of anti-histamine drugs which would just target the immediate reaction (ie: use for hay fever/allergic rhinitis)
What is atopy
Increased propensity to develop immediate hypersensitivity reactions
What are some characteristics that atopic individuals tend to h ave
Higher serum IgE levels and more IL-4 producing Th2 cells; positive family history of allergy
Genes encoded on what chromosome are linked to familial predisposition to allergies
5q31; include genes that encode for IL-3,4,5,9,13, and GM-CSF
Besides genetics, what is important in the development of allergies
Environmental factors
What is nonatopic allergy
Immediate hypersensitivy reaction triggered b y non-antigenic stimuli such as temperature extremes and exercise; no Th2 or IgE; mast cells are abnormally sensitive to activation
What has the increase in presence of allergic diseases been linked to
Decrease in infections during early life; hygiene hypothesis -> early exposure to microbial antigens educates the immune system so that subsequent pathological responses against common allergens are prevented
What occurs during systemic anaphylaxis
Within minutes: itching, hives and skin erythema, followed by contraction of respiratory bronchioles, then laryngeal edema, vomiting, abdominal cramps, diarrhea, and laryngeal obstruction flow
What is antibody-dependent cellular cytotoxicity
Cells that are coated with IgG ab are killed by NK and macrophages which bind to the starter via their Fc fragment of IgG; cell lysis occurs
What kind of hypersensitivity is transfusion reactions
II; cells from incompatible donor react with an are opsonized by preformed ab in the host
What kind of hypersensitivity reaction is hemolytic disease of the newborn (erythroblastosis fetalis)
II; IgG anti-Erythrocyte abs from the other cross the placenta and destroy fetal RBCs
What is autoimmune hemolytic anemia, agranulocytosis and thrombocytopenia
Individuals produce abs to their own blood cells -> type II
What are drug reactions, where the drug acts as a happen
Drug binds to the plasma membrane of RBCs -> abs produced agains the drug-protein complex; type II
What happens when ab deposit in fixed tissues
Ie: basement membrane and extracellular matrix; resultant injury due to inflammation; activate complement which recruits leukocytes, which are activated by their C3b and Fc receptors; this releases production of lysosomal enzymes (proteases that can digest basement membrane) and ROS; mechanism responsible in glomerulonephritis and vascular rejection in organ grafts; type II
How can type II hypersensitivity impair cellular function
Abs to cell surface receptors; Ie: myasthenia gravis -> abs to Ach receptors in motor end plates of skeletal mm causes m weakness; also, Graves’ disease -> ab to TSH receptor activates the receptor and results in hyperthyroidism
What is the target antigen in autoimmune thrombocytopenia purpura
Platelet membrane proteins (GpIIb:IIIa); causes opsonization of phagocytosis of platelets -> bleeding
What is pemphigus vulgaris
Targeted antigen -> proteins in intercellular junctions of epidermal cells (cadherin); causes ab mediated activation of proteases and disruption of cellular adhesions -> skin vesicles (Bullae) form (type II)
What is targeted in goodpasture syndrome
Noncollagenous protein in basement membrane of kidney glomeruli and lung alveoli; causes complement and Fc receptor mediated inflammation -> nephritis and lung hemorrhage (type II)
What is the target antigen in acute rheumatic fever
Streptococcal cell wall antigen; ab cross reacts with myocardial antigen -> inflammation and macrophage activation -> myocarditis and arthritis
What kind of hypersensitivity reaction is type II diabetes
II; targets insulin receptor -> ab inhibits binding of insulin
What is targeted in pernicious anemia
Intrinsic factor of gastric parietal cells -> causes neutralization of IF which causes decreased absorption of B12 -> abnormal erythropoiesis and anemia
What are common characteristics of type III (immune complex mediated) hypersensitivity
Systemic, preferentially involving kidney, joints, and small vessels
What are the phases of systemic immune compiles disease
- Formation of immune complexes: intro of a protein triggers production of abs, typically about a week after injection; complexes form
- deposition of complexes (medium sized with slight antigen excess are most pathogenic); organs where blood is filtered at high pressure to form other fluid (urine and synovial fluid) are where they become concentrated and deposit
- inflammation and tissue injury: imitation acute inflammatory reaction (approx 10 days after administration); causes fever, urticaria, joint pains (arthralgias), LN enlargement and proteinuria
Which abs are involved in immune complex disorders
IgG and IgM
How do we know that complement proteins are significant in type III hypersensitivity
Consumption of complement leads to decrease in serum C3 levels
What is the morphology of immune complex injury
Acute vasculitis, necrosis of vessel wall and intense neutrophilic infiltration; *fibrinoid necrosis (appears smudgy eosinophilic areas)
What is the arthus reaction
Localized area of tissue necrosis caused by acute immune complex vasculitis in the skin; can be produced by injection of an antigen in a previously immunized animal that contains circulating abs for that antigen
What is the prototype of CD4 T cell mediated inflammation
Delayed type hypersensitivity: tissue reaction to immune individuals; administration of an antigen results in cutaneous reaction within 24-48 hours (delayed)
What are the stages of CD4 mediated inflammation
Activation of T cells: naive CD4 T cells recognize antigen and produce IL2; if APC produces IL-12 -> Th1; if IL-1,6,or 23 then Th17 Responses of effector cells: repeat exposure to antigen, TH1 secretes IFN-y; causes macrophages to express more class II MHC which facilitates further presentation, secrete TNF, IL1 and chemokines to promote inflammation and IL12 to amplify Th1 response; Th17 produce IL-17 and 22 -> neutrophils and monocytes
What are examples of T cell mediated diseases
Rheumatoid arthritis, MS, T1DM, IBD, psoriasis, contact sensitivity
What is the target antigen in MS
Myelin; inflammation by Th1 and 17; myelin destruction by macrophages
What is tuberculin reaction an example of
CD4 mediated inflammatory reaction (delayed type hypersensitivity)
Describe what the tuberculin reaction is
Intracutaneous injection of purified protein derivative (PPD) containing the antigen of tubercle bascillus; in a previously sensitized individual, injection causes redness and induration of the site in 8-12 hours, peak in 24-72 hours and then subsides
Morphologically, what are DTH reactions characterized by
CD4 T cells and macrophages accumulated around venules, producing perivascular cuffing; in fully developed lesions -> venules show endothelial hypertrophy (cytosine mediated endothelial activation)
What are granulomatous inflammation associated with
Strong Th1 cell activation and high levels of IFN-y
How does contact dermatitis work
Environmental chemical binds to and modifies some self proteins -> peptides derived from these modified proteins are recognized by T cells and elicit the reaction; chemicals can also modify HLA molecules, making them appear foreign; same mechanism used for most drug reactions
What is an example of CD8 T cell mediated cytotoxicity disease
T1DM, graft rejection
What are the requirements that must be met to diagnose an autoimmune disorder
Presence of an immune reaction specific for some self antigen or self tissue, evidence that such a reaction is not secondary to tissue damage, and the absence of another well-defined cause of the disease
What are the organ specific autoimmune diseases mediated by abs
Autoimmune Hemolytic anemia, thrombocytopenia, atrophic gastritis of pernicious anemia, myasthenia gravis, Graves’ disease, good pasture syndrome
What the organ specific autoimmune diseases. Mediated by T cells
T1DM, MS
What are the systemic autoimmune diseases mediated by abs
SLE
What are the systemic autoimmune diseases mediated by T cells
Rheumatoid arthritis, sjogren syndrome, and systemic sclerosis (scleroderma)
What is central tolerance
Immature self reactive T and B clones that recognize self antigens during their maturation in generative lymphoid organs are killed
Describe the central tolerance process for T cells
When immature T cells recognize a self antigenmany die by apoptosis (negative selection or deletion); AIRE (autoimmune regulator) stimulates expression of peripheral tissue-restricted self ags in the thymus (mutation causes autoimmune polyendocrinopathy); some develop into Treg cells
Describe central tolerance in B cells
When B cells recognize self antigens, many of the cells reactivate the machinery for antigen receptor gene rearrangement and begin to express new antigen receptors (receptor editing), if this does not occur, they undergo apoptosis
What is anergy
Self reactive T cells are rendered unresponsive; costimulators (B7) are weakly expressed on normal tissues; thus the self reactive T cells will not have the costimulation needed and become anergic; also,these cells receive inhibitory signals from CTLA4 (which has a higher affinity for B7 and are therefore more likely to bind)
What are antibodies that block CTLA-4 and PD-1 used for
Treat tumor immunotherapy; promotes response against tumors
How does anergy affect B cells
If B cells encounter self antigen in peripheral tissues (especially in absence of T helper cells), B cells become usable to response and may be excluded from lymphoid follicles (resulting in their death)
What are the best defined T reg cells
CD4 cells that express high levels of CD25, the alpha chain of the IL-2 receptor, and FOXP3
What does mutation of FOXP3 cause in humans
IPEX (Immune dysregulation polyendocrinopathy, enteropathy, X-linked)
Which IL is essential for maintenance of T reg cells
IL-2
How to Treg cells suppress immune responses
Secrete IL-10 and TGFbeta, also express CTLA-4, which may bind to B7 on APCs and reduce the amount of B7 that can bind to CD28
How do self reactive T cells die by apoptosis
If T cells recognize a self antigen, they express a pro-apoptotic member of BCL family, called Bim without anti apoptotic members (antiapoptotic require full lymphocyte signaling to be activated); Bim triggers apoptosis by mitochondrial pathway; also CD4+ and B cells can die by Fas-FasL apoptosis (both are expressed on self reactive cells)
A mutation in FAS causes what disease
autoimmune lymphoproliferative syndrome (ALPS)
What are the immune privileged sites
Brain, eye, testis; antigens do not communicate with blood or lymph; therefore if antigens released by trauma, causes prolonged immune response; mechanism for post-traumatic orchitis and uveitis
What is inheritance of HLA-B27 linked to
Ankylosing spondylitis
What is inheritence of DQA1 and DQB1 associated with
Celiac disease
What is inheritence of DRB1 associated with
MS, T1DM, rheumatoid arthritis and SLE
What are polymorphisms in PTPN22 associated with
Encodes a protein tyrosine phosphatase; associated with T1DM, rheumatoid arthritis, and other autoimmune dz *gene most frequently implicated in autoimmunity; encodes for a phosphatase that is functionally defective and cannot control activity of RTK (excessive lymphocyte activation)
What are polymorphisms of NOD2 associated with
Crohn dz; cytoplasmic receptor; dz variant is ineffective at sensing gut microbes, including commensal bacteria, which results in entry of and chronic inflammatory responses against these organisms
What are polymorphisms in the IL-2 receptor (CD25) and IL-7 receptor alpha chains associated with
MS
What does a knockout of the IgG Fc receptor on B cells cause
Autoimmunity; binding of IgG/ab complexes to the Fc receptor on B cells turns the B cells off; thus, B cells can no longer be controlled d
How do infections trigger autoimmune responses
Infections upregulate the expression of costimulators on APCs (breakdown of anergy b/c no self reactive T cells can react); also microbes can express antigens that have the same AA sequences as self antigens (molecular mimicry)
What is an example of molecular mimicry
Rheumatic heart disease; abs against strep cross react with myocardial proteins and cause myocarditis
How do Epstein Barr virus and HIV influence autoimmune reactions
Stimulate polyclonal B cell. Activation, which can result in auto-ab production
How can infections protect against some autoimmune diseases
Infections promote low level IL-2 production which maintains T reg cells
What role does IL23R play in autoimmune disease
Associated wtih IBD, psoriasis, and akylosing spondylitis; receptor for IL-23 (induced by Th17); alters differentiation of CD4 to Th17 effector cells
What is epitope spreading
An immune response against one self antigen cases tissue damage, releasing other antigens, resulting in activation of lymphocytes by these newly encountered epitopes
In T1DM, what kind of autoimmune reactions is involved in killing the beta cells
CD8 CTLs
Are abs or T cells involved in rheumatoid arthritis
Both
What do systemic autoimmune diseases tend to target
Blood vessels and connective tissue; therefore called collagen vascular diseases or connective tissue diseases
Who is most susceptible to SLE
Women between the ages of 17-55, blacks and Hispanics; however, can manifest at any age
What are the categories of antinuclear antibodies
Abs to DNA, abs to histones, abs to non histone proteins bound to RNA, and abs to nucleolar antigens
What is the method used to detect ANAs
Indirect immunofluorescence; can identify abs bound to a variety of nuclear antigens (DNA, RNA, proteins - called generic ANAs); pattern of fluorescence suggests type of ab present in patients serum
What are the listed criteria for SLE
Malar rash, discoid rash, photosenstivity, oral ulcers, arthritis, serositis, renal disorder, neurological disorder, hematologic disorder, immunologic disorder, antinuclear ab
What is a malar rash
Flat or raised over malar eminences, tends to spare nasolabial folds
What is a discoid rash
Erythematous raised patches with adherent keratitic scaling and follicular plugging; atrophic scarring can occur in older lesions
What is the arthritis criteria for SLE
Nonerosive arthritis involving 2 or more peripheral joints, characterized by tenderness, swelling, or effusion
What is the renal disorder criteria for SLE
Persistent proteinuria >.5 g/dL or cellular casts (RBC, hemoglobin, granular, tubular or mixed)
What is involved in the neurological criteria for SLE
Seizures in the absence of offending drugs or known metabolic derangement (ketoacidosis, uremia, or electrolyte imbalances) or psychosis in the absence of offending drugs or known metabolic derangements
What is involved in the hematologic criteria for SLE
Hemolytic anemia with reticulocytosis or leukopenia, lymphopenia, or thrombocytopenia on two or more occasions in the absence of offending drugs
What are the basic patterns displayed in indirect immunofluorescence when testing for ANAs
- Homogeneous or diffuse nuclear staining: abs to chromatin, histones, and dsDNA
- Rim or peripheral staining: abs to dsDNA and nuclear envelope proteins
- Speckled pattern: *most common so least specific; abs to non-DNA nuclear constituents such as SM antigen, ribonucleoprotein, and SS-A/B reactive antigens
- Nucleolar pattern: presence of few discrete spots within nucleus; abs to RNA *reported most often in patients with systemic sclerosis
- Centromeric pattern: abs to centromeres; also seen in systemic sclerosis
Abs to what are virtually diagnostic of SLE
dsDNA and smith antigen (speckled pattern and homogenous)
What are the targets of the antiphospholipid abs in SLE
Prothrombin, annexin V, beta2 glycoprotein I, protein S, and protein C
What does the ab to phospholipid beta2 glycoprotein also bind to
Cardiolipin antigen -> used for syphilis testing
Which clotting test do the abs present in lupus alter
PTT in vitro (lupus anticoagulant); but in vivo, actually cause hypercoaguability
What disease feature is linked to abs to dsDNA in SLE
Nephritis; specific for SLE
What disease feature are abs to SS-A (Ro) and SS-B (La) linked to in SLE
Congenital heart block, neonatal lupus
Abs to what are associated with systemic sclerosis
- DNA topoisomerase I (linked to diffuse skin and lung disease; specific for systemic sclerosis)
- Centromeric proteins (CENPs) ABC (linked to skin disease, ischemic digit loss, pulm HTN)
- RNA polymerase III (linked to acute onset, scleroderma renal crisis, cancer)
Abs to what are linked to Sjogren syndrome
SS-A/B
Abs to what are associated with autoimmune myositis
- Histidyl aminoacyl-tRNA synthetase, Jo1 (linked to interstitial lung dz, Raynaud phenomenon)
- Mi-2 nuclear antigen (linked to dermatomyositis, skin rash)
- MDA5 (cytoplasmic receptor for viral RNA) - linked to vascular skin lesions, interstitial lung dz
- TIF1-y nuclear protein (linked to dermatomyositis, cancer)
Abs to what are linked to rheumatoid arthritis
CCP (cyclic citrullinated peptides): specific for RA
Rheumatoid factor
Alleles of the HLA-DQ locus have been linked to production of abs against what
DsDNA, smith, and phospholipids
What is the involvement of complement in SLE
May have inherited deficiencies in early complement (C2,4, or C1q); lack of complement can impair removal of circulating immune complexes by phagocytes -> this favors tissue deposition; deficiency in C1q causes defective phagocytic clearance of apoptotic cells
Are the abs produced in SLE T cell dependent or independent
Dependent; produced in germinal centers; increased number of follicular helper T cells found in blood of SLE patients
What is the role of type I IFN in SLE
Lymphocytes activation; high levels of circulating type I IFN correlates with disease severity; type I IFNs are antiviral cytokines normally produced by innate immunity (in SLE could be caused by nuclear DNA binding to TLRs and causing dendritic cells to produce IFN)
What is BAFF
TNF family member that promotes survival of B cells; in some SLE patients, increased BAFF has been detected
How does exposure to UV light relate to SLE
May induce apoptosis and alter DNA in such a way that it becomes immunogenic (enhances recognition by TLRs); can also stimulate keratinocytes to produce IL-1
Which drugs can induce SLE-like response
Hydralizine, procainamide, isoniazid, and D-penicillamine
In SLE, what do auto-abs to RBC, WBC, an platelets do
Opsonize them and promote their phagocytosis and lysis
What are LE cells
Cells that have engulfed denatured nucleus of another cell; present in lupus (as well as pericardial or pleural effusions)
What does SLE do to blood vessels
Acute necrotizing vasculitis involving capillaries, small arteries, and arterioles can be present in any tissue; characterized by fibrinoid deposits; chronically, undergo vessel thickening and narrowing
Where do the immune complexes generally deposit in the kidney in SLE
Mesangium, basement membrane
What are the six patterns of glomerular disease found in SLE
Minimal mesangial lupus nephritis, mesangial proliferative, focal, diffuse, membraneous, advanced sclerosing *can advance to other stages; class I least common, class IV most common
What is minimal mesangial lupus nephritis
Class I: characterized b y immune complex deposition in the mesangium, identified by immunofluorescence and EM, but without structural changes by light microscopy
What is mesangial proliferative lupus nephritis
Class II: characterized by mesangial cell proliferation, accompanied by accumulation of mesangial matrix and granular mesangial deposits of Ig and complement without involvement of glomerular capillaries
What is focal lupus nephritis
Class III: involvement of few than 50% of all glomeruli; can be segmental (only portion of glomeruli affected) or global (entire glomerulus); affected glomeruli exhibit swelling and proliferation of endothelial and mesangial cells associated with leukocyte accumulation, capillary necrosis, and hyaline thrombi; often extracapillary proliferation and focal necrosis and crescent formation; clinical presentation can range from mild hematuria and proteinuria to acute renal insufficiency; red cast cells common; can heal or progress
What is diffuse lupus nephritis
Class IV: *most common and severe; lesions similar to class III; half or more of glomeruli are affected; may be segmental or global (IV-s or IV-G); proliferation of endothelial, mesangial and epithelial cells (produces cellular crescents that fill Bowmans space); subendothelial immune complex deposition creates a wire loop (circumferential thickening of capillary Wall seen on light microscopy); immune complexes detected by EM and immunofluorescence; can progress to scarring; usually symptomatic (hematuria and proteinuria; also HTN common)
What is membraneous lupus nephritis
Class V: diffuse thickening of capillary walls due to deposition of subepithelial immune complexes, usually accompanied by increased production of basement membrane-like material; accompanied by severe proteinuria or nephrotic syndrome; can occur concurrently with diffuse or focal lupus nephritis
What is advanced sclerosing lupus nephritis
Class VI: characterized by sclerosis of more than 90% of glomeruli; represents end stage renal disease
What do the skin changes in SLE show histologically
Vascular degeneration of the basal layer of the pidermis; in dermis, variable edema and perivascular inflammation
What SLE skin changes can you see on immunofluorescence
Deposition of immune complexes and complement along dermoepidermal junction in involved and uninvolved skin; not diagnostic of SLE (may also be seen in scleroderma and dermatomyositis))
What is different about the vegetations found in endocarditis in Libman Sacks versus infective endocarditis and rheumatic heart disease
Infective endocarditis the vegetations are larger; rheumatic heart disease are smaller
When is coronary artery disease seen in SLE patients
More common in young patients with noteable disease and especially prevalent in those who ha ve been treated with corticosteroids
What are common SLE affects seen in the spleen
Splenomegaly, capsular thickening, and follicular hyperplasia; central penicilliary arteries can show concentric intimacy and smooth m cell hyerplasia producing onion-skin lesions
What happens during acute flare ups of SLE
Increased formation of immune complexes and complement activation leads to hypocomplementemia; treated with corticosteroids or other immunosuppressants
What are the most common causes of death in SLE patients
Renal failure and inter current infections
What is chronic discoid LE
Skin manifestations mimic SLE, but systemic manifestations are rare; characterized by skin plaques showing edema, erythema, scaliness, follicular plugging, and skin atrophy surrounded by an elevated border; usually affects face and scalp; ANAs involved but rarely have abs to dsDNA; immunofluorescence shoes depositin of Ig and C3 at the dermoepidermal junction, similar to SLE
What is subacute cutaneous LE
Skin involvement, distinguished from discoid by: widespread, superficial, nonscarring; mild systemic symptoms consistent with SLE; association with abs to SS-A antigen and with HLA-DR3 genotype
What kind of treatment induces drug induced LE
Anti-TNF treatment (used to treat RA)
Do people with drug induced LE normally have symptoms
No, but tests positive for ANAs; those that do manifest symptoms such as fever, arthralgias, and serositis; renal and CNS involvement is highly uncommon
What abs are commonly seen in drug induced LE
Abs to histones; dsDNA is rare
People with what allele are at greater risk for developing LE-like syndrome after administration of hydralazine
HLA-DR4
People with what allele are at greater risk for developing LE-like syndrome after administration of procainamide
HLA-DR6
What is sjogren syndrome
Characterized by dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia) resulting from immunologically mediated destruction of lacrimal and salivary glands; can occur in primary form (isolated disorder) or in association with another autoimmune dz (secondary form) *RA most common associated disorder
What is the mechanism of sjogren syndrome
Lymphocytic infiltration and fibrosis of lacrimal and salivary glands; CD4 helper cells and B cells/plasma cells
What abs are found in sjogren syndrome
Rheumatic factor (ab to IgG), ANAs, *most impt -> abs against SS-A and SS-B (markers of disease) - those with SS-A more likely to have early onset of dz, longer duration, and extraglandular manifestations (cutaneous vasculitis and nephritis), however not diagnostic of the dz
What is the primary form of sjogren syndrome linked to, genetically
HLA-B8, DR3, DRW52,
*DQA1, and DQB1 -> patients with SS-A and B abs, this is frequent
What is the earliest histological finding in Sjogren syndrome
Periodical and perivascular lymphocyte infiltration; as time goes on, germinal centers may be present in larger salivary glands, ductal lining epithelial cells can show hyperplasia (obstructs ducts); later will see atrophy fibrosis and hyalinization; lastly replacement of parenchyma with fat
What are people with sjogren syndrome at risk for
B cell lymphomas
What are the clinical manifestations of sjogren syndrome
Inflamed, eroded, and ulcerated corneal epithelium; atrophy of oral mucosa with inflammatory fissuring and ulceration, ulceration and perforation of nasal septum; blurring of vision, burning and itching, thick secretions accumulate in conjunctival sac, difficulty swallowing, decreased ability to taste, epistaxis, enlargement of parotid gland, recurrent bronchitis and pneumonia is
What population does sjogren syndrome occur most frequently in
Women between ages of 50 and 60
What are the extraglandular manifestations seen in sjogren syndrome
Synovitis, diffuse pulmonary fibrosis, and periphery neuropathy; more common with high titers of SS-A abs; glomerular lesions highly rare; however defects in tubular function are seen (renal tubular acidosis, uricosuria, and phophaturia -> associated with tubulointerstitial nephritis)
What is mikulicz syndrome
Lacrimal and salivary gland enlargement due to any cause including sarcoidosis, lymphoma, and other tumors
What is essential for diagnosis of sjogren syndreom
Biopsy of the lip to examine minor salivary glands
Overtime, what can happen to the B cells of someone with sjogren syndrome
B cell clones can gain a growth advantage (presumably due to acquisition of somatic mutation); dominant B cell. Clones is indicative of development of marginal zone lymphoma (hashimoto thyroiditis is also associated with this lymphoma)
What is systemic sclerosis (scleroderma)
Characterized by chronic inflammation due to autoimmunity, damage to small blood vessels, and progressive interstitial and perivascular fibrosis in the skin and multiple organs; remains in skin for many years but ultimately progresses to visceral; death from renal, cardiac, or pulmonary failure or intestinal malabsorption
What are the two categories of scleroderma
Diffuse scleroderma: widespread skin involvement at onset with rapid progression and early visceral involvement
Limited scleroderma: skin involvement is confided to fingers, forearms and face; visceral involvement occurs late; relatively benign
What do patients with limited scleroderma also often develop
Combination of calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly and telangiectasia(dilated small bv) (CREST syndrome)
What are the 3 processes that combine to cause scleroderma
Autoimmune responses, vascular damage, collagen deposition
Which cells are involved in the autoimmune reaction in scleroderma
CD4 and Th2 cells -> IL-13 and TGFbeta stimulate collagen deposition; also inappropriate activation of humoral immunity (ANAs produced)
Describe the vascular damage seen in scleroderma
Microvascular disease consistently present early on; may be primary lesion; intimal proliferation is evident in digital arteries, capillary dilation with leaking, and nail fold capillary loops are distorted in early course and eventually disappear; * have telltale signs of endothelial activation (ie: increased levels of vWF) and increased platelet activation; repeat injury and platelet aggregation causes release of PDGF and TGFbeta causing perivascular fibrosis; vascular smooth m shows increased adrenergic receptors as well
What causes the fibrosis in scleroderma
Accumulation of M2 macrophages, hyperresponsiveness of fibroblasts to cytokines released by infiltrating leukocytes, scarring following ischemic damage caused by vascular lesions; *evidence that patients have abnormality with fibroblasts that cause them to produce excessive collagen
Describe the skin involvement in scleroderma
Sclerotic atrophy usually begins distally (fingers) and works proximally (shoulders, neck, face); histo: edema and perivascular infiltrates containing CD4 cells w/ swelling and degeneration of collagen; with progression, increasing fibrosis of the dermis and thinning of epidermis; sometimes leads to autoamputation; face becomes drawn mask
What happens to the alimentary tract with scleroderma
PRogressive atrophy and collegeneous fibrous replacement of the muscularis (most severe in esophagus) -> lower 2/3 develops rubber-hose-like inflexibility -> leads to GERD and Barrets metaplasia; loss of villi in small bowel (malabsorption)
What is the involvement of the MSK system in scleroderma
Inflammation of synovium associated with hypertrophy and hyperplasia of synovial soft tissue in the early stages; fibrosis later; reminiscent of RA, but joint destruction is not common; in some patients, inflammatory myositis (indistinguishable from polymyosistis) may develop
What happens to the kidneys in scleroderma
Vascular lesions; resembles malignant hypertension, but scleroderma only involves vessels 150-500 micrometers in diameter and doesn’t always involve HTN; 50% of patients die of renal failure
What is the involvement of the lungs in scleroderma
May involve pulm HTN (pulm vasospasm secondary to pulm vascular endothelial dysfunction) or interstitial fibrosis
What is the heart involvement in scleroderma
Pericarditis with effusion, myocardial fibrosis, thickening of intramyocardial arterioles
What are the clinical features of scleroderma
Female to male ratio is 3:1; peak incidence in 50-60 yrs old; distinct features: skin thickening, Raynauds, dysphasia, ab pain, malabsorption, anemia, resp difficulties, malignant hypertension; more severe in black women; pulm death has been main cause since renal treatments have improved
What are the two ANAs specific for scleroderma
DNA topoisomerase I (anti-Scl 70) - more likely to have pulm fibrosis and PVD; and anticentromere ab: tend to have CREST syndrome -> limited involvement of skin; live longer
What are examples of inflammatory myophathies
Dermatomyositis, polymyositis, and inclusion body myositis
What are mixed connective tissue diseases
Have clinical features that are a mix of SLE, systemic sclerosis, and polymyositis; characterized by high titers of abs to ribonucleoprotein particle-containing U1 ribonucleoprotein; present with synovitis of fingers, Raynaud and mild myositis; renal involvement modest; good response to steroids; can evolve into classic SLE or scleroderma
What is noninfections vasculitis
Includes polyarteritis nodosa; necrotizing inflammation of walls of any bv
What diseases are considered IgG4-related diseases
Mikulicz (enlargement and fibrosis of salivary and lacrimal glands), diesel thyroiditis, idiopathic retroperitoneal fibrosis, autoimmune pancreatitis and inflammatory pseudo tumors of the orbit, lungs, and kidneys; most often effects middle aged and older men
What is rituximab
Anti-b cell reagent
Describe the direct pathway of allorecognition
T cells of recipient recognize donor MHC molecules on APCs in the graft (dendritic cells in the donor organs are most impt for initiating antigraft response); CD8 and CD4 cells recognize molecules
Describe the indirect pathway of allorecognition
Recipient T cells recognize MHC antigens of the graft being presented by the recipients APCs; generates CD4 cell that enter the graft -> delayed hypersensitivity reaction; CD8 cells that are generated cannot kill graft cells because they recognize graft antigens presented by host APCs and cannot recognize graft cells directly
What is stronger - immune responses to allografts or to microbes
Allografts
Describe what occurs in acute cellular rejection
CD4 cells react by secreting cytokines and causing inflammation; causes increased vascular permeability and local accumulation of mononuclear cells; graft injury is caused by activated macrophages
How do T cells contribute to chronic rejection
Lymphocytes in the vessel wall secrete cytokines that induce local inflammation and stimulate the proliferation of vascular endothelial cells and smooth m cells
Describe how abs are involved in hyperacute rejection
Preformed abs against the donor antigens are present in the circulation of the recipient ie: someone who has previously rejected a transplant, multiparous women who develops abs against parental HLA antigens (reject from husband or children), prior blood transfusion
How are abs involved in acute ab mediated rejection
Anti donor abs produced after transplantation; cause injury by complement dependent cytotoxicity, inflammation, and ab dependent cell mediated cytotoxicity; initial target seems to be graft vasculature
How are abs involved in chronic ab mediated rejection
Develops without preceding acute rejection and primarily affects vasculature; abs detected but not readily identified within the graft; not well understood
Describe what happens to a hyperacute rejected kidney
Within minutes to hours becomes cyanotic, mottled, and flaccid, may excrete few drops of blood urine; Ig and complement deposited in vessel walls causing injury and fibrin-platelet thrombi, neutrophils accumulate; glomeruli undergo thrombotic occlusion of capillaries and fibrinoid necrosis occurs; kidney cortex undergoes necrosis (infarction) and has to be removed
Describe what happens to an acute rejected kidney
Within days, weeks, months, or even years; T cell or B cells can predominate depending on individual
Describe the different patterns of T cell mediated acute rejection of the kidney
Tubulointerstitial: type I, interstitial inflammation with infiltration of tubules (tubulitis), both CD4 and CD8 cells present
Vascular: type II; endotheliitis; necrosis of vascular walls(type III), swollen endothelial cells; important to recognize because in absence of humoral rejection, patients respond well to immunosuppressive therapy
What effect can cyclosporine have
Nephrotoxic so can cause histological changes like arteriolar hyaline deposits
What occurs during chronic rejection of the kidney
Dominated by vascular changes; intimal thickening w/inflammation, glomerulopathy w/ duplication of basement membrane, peritubular capillaries; have mononuclear infiltrated include NK and plasma cells
What are the immunosuppressive drugs used for transplant
Steroids, mycophenolate mofetil (inhibits lymphocyte proliferation), tacrolimus (predecessor is cyclosporine; inhibitor of phosphatase calcineurin which activates TF, NFAT)
What are individuals on immunosuppressive therapy for transplants at risk for
EBV induced lymphomas, HPV induced squamous cell carcinomas, and kaposi sarcoma
Describe acute GVHD
Occurs within days to weeks; major manifestation results in involvement of the immune system of the skin, liver, and intestines; generalized rash, destruction of small bile ducts (jaundice) and mucosal ulceration of gut (bloody diarrhea); tissue not heavily infiltrated by lymphocytes; CD8 and CD4 cells of donor responsible
Describe chronic GVHD
Extensive cutaneous injury, destruction of skin appendages, fibrosis of dermis (Resembles sclerosis), cholestatic jaundice (chronic liver disease), esophageal strictures, involution of thymus and depletion of lymphocytes in LN (recurrent infections)
How can you prevent GVHD
Removing T cells from donor; however, in HSC transplants for leukemia patients, will cause recurrence of tumors and increased risk of graft failure and EBV related B cell lymphoma
What is a complication of HSC transplant
Immunodeficiency; *infection with cytomegalovirus is impt -> induced pneumonia can be fatal
What is the difference between primary and secondary immunodeficiency syndromes
Primary: genetic
Secondary: acquired
Describe inherited defects in leukocyte adhesion
- leukocyte adhesion deficiency type I: defect in synthesis of beta2 chain shared by LFA-1 and Mac-1 integrins
- leukocyte adhesion deficiency type II: absence of sialyl Lewis X (ligand for E and P selectin) -> caused by defect in fucosyl transferase
- both of these cause recurrent bacterial infections due to inadequate granulocyte function
Describe inherited defects in phagolysosome function
*chediak-higashi syndrome; AR; defective fusion of phagosomes and lysosomes; causes neutropenia (decreased neutrophils), defective granulation, delayed microbial killing; peripheral blood smears reveal leukocytes containing giant granules; abnormalities in melanocytes (albinism), cells of the nervous system, and platelets (bleeding disorders); defective gene encodes for LYST, which regulates lysosomal trafficking
Describe defects in microbicidal activity
*chronic granulomatous disease; susceptible to bacterial infections; defects in genes encoding for phagocyte oxidase (generates superoxide anion); most common are x-linked defect in one of the membrane components (gp91phox) and AR defects in genes encoding cytoplasmic components (p47phox and p67phox)
Describe defects in TLR signaling
Defects in TLR3 (for viral RNA) -> recurrent herpes simplex encephalitis
Defects in MyD88 -> adaptor protein downstream; destructive bacterial pneumonia’s
What is the most common complement protein deficiency
C2
What is a deficiency of C2 or 4 associated with
Recurrent bacterial or viral infections; but patients usually have no symptoms because alternative pathway can still function; but can cause SLE-like autoimmune disease
What is deficiencies of the alternative complement pathway associated with
(Properdin and factor D); associated with pyogenic infections.
What does a deficiency of C5-9 associated with
Recurrent neisserial infections (gonococcal and meningococcal)
What inheritance pattern does hereditary angioedema have
AD
What are the targets of C1 inhibitor
C1r, C1s, factor XII, and kallikrein system; unregulated activity of kallikrein leads to increased production of bradykinin
What is severe combined immunodeficiency
SCID: defects in humoral and cell-mediated immune responses; infants present with thrush, diaper rash and failure to thrive; some develop morbilliform rash after birth (maternal T cells cross placenta and attack fetus); susceptible to Candida albicans, pneumocytosis jiroveci, pseudomonas, cytomegalovirus, varicella; without HSC transplant, death occurs within 1st year
What is the most common form of SCID
X-linked; *more common in boys; mutated gamma chain subunit of cytokine receptors for IL-2,4,7,9,11,15,and21; IL-7 required for survival of lymphoid progenitors (T cell precursors); T cells decreased, B cell numbers normal but ab synthesis decreased; also deficient in NK cells (lack of IL-15)
Describe AR SCID
Most common cause results from deficiency of adenosine deaminase (ADA); accumulation of deoxyadenosine toxic to immature lymphocytes; also proposed mechanisms: mutation in recombinant activating genes (RAG) ->blocks development of T and B cells; mutations of Jak3, and mutations of kinases or calcium channels
Describe the histological changes in SCID
In gamma mutation and ADA deficiency: thymus is small and devoid of lymphoid cells; former, thymus has lobules of undifferentiated epithelial cells (Fetal thymus); later: remnants of Hassals corpuscles can be found
What is a risk to the HSC transplant used for SCID
Development of T cell lymphoblastic leukemia
What is X-linked agammaglobulinemia
Characterized by failure of B cell precursors to develop into mature B cells; caused by mutations in cytoplasmic TK (Bruton TK) located on long arm of Xq21.22; Btk is associated with Ig receptor complex -> needed to transduce signals; mutation causes inability for pre-b cell to deliver signals and maturation stops; light chains are not produced
When does X-linked agammaglobulinemia become apparent
About 6 months, when maternal abs have depleted; manifests as recurrent bacterial infections of upper respiratory tract
What are the causative organisms of the recurrent infections seen in x-linked agammaglobulinemia
Haemophilus influenzae, streptococcus pneumoniae or staphylococcus aureus; they are normally opsonized by abs and cleared; *also viral infections especially enteroviruses (echovirus, poliovirus, and coxsackievirus); giardia lamblia (intestinal protozoan resisted by IgA) also seen in this disorder; *intracellular infections, however, are handled quite well
What are the characteristics of the classic form of X-linked agammaglobulinemia
B cells absent, all classes of Igs are decreased, pre B cells (CD19 marker) w/o Igs are in normal numbers, germinal centers, peyer’s patches, the appedix and tonsils are all underdeveloped; plasma cells absent; T cell mediated reactions normal
Why are autoimmune diseases common in X-linked agammaglobulinema
Breakdown of self-tolerance
How do you treat X-linked agammaglobulinemia
Ig replacement therapy
DiGeorge syndrome is a deficiency of what?
T cells; poor defense against viral and fungal infections
Describe the characteristics of DiGeorge syndreom
T cell zones of lymphoid organs (paracortical areas of LN and periarteriolar sheaths of spleen) are depleted, Ig levels can be normal or reduced
What gene is encoded for in the 22q11 chromosome
TBX1 -> required for development of the branchial arch and great vessels; involved by loss-of-function mutations that lack the 22q11 deletion in DiGeorge
What is bare lymphocyte syndreom
Mutation in TF that are required for class II MHC gene expression; this prevents development of CD4 cells and then B cells cant be activated -> results in combined immunodeficiency
What causes hyper-IgM syndrome
X-linked form: mutation of gene encoding CD40L on Xq26
AR form: loss-of-function mutations invovling either CD40 or activation-induced cytidine desminase (AID) -> DNA editing enzyme required for Ig switching and affinity maturation
What are the characteristics of hyper-IgM syndreom
High IgM, no IgA or IgE, low levels of IgG; B and T cells normal; recurrent pyogenic infections (opsonizing IgG abs is low); those with CD40L mutations are susceptible to pneumonia caused by the intracellular organism, pneumocystis jiroveci because cannot activate macrophages; IgM can react w/ blood cells and cause autoimmune hemolytic anemia, thrombocytopenia, and neutropenia
What is common variable immunodeficiency
Encompasses group of disorders in which the common feature is hypogammaglobulinemia (generally all classes but sometimes just IgG); both sporadic and inherited forms; normal B cells that cannot differentiate into plasma cells; some have defect in BAFF receptor which promotes differentiation of B cells or ICOS which is homologous to CD28
What are the clinical manifestations of common variable immunodeficiency
Resemble X-linked agammaglobulinemia because no abs produced; recurrent sinopulmonary pyogenic infections and herpesvirus infections; *affects both sexes equally and onset is later than agammaglobulinemia; B cell areas are hyperplastic; high frequency of autoimmune disease; risk of lymphoid malignancy and increase in gastric cancer
What is isolated IgA deficiency
*european descent; low levels of secretory and serum IgA; can be acquired (associated with viral infection - measles) or genetic; asymptomatic; mucosal defense weakened (infections occur in resp, GI, and GU tracts); those with defects in IgG2/4 are particularly prone to infections; prone to AI dz (SLE) and resp allergy
What can happen when infusing IgA into people with IgA deficiency
Can have severe anaphylactic reaction; IgA behaves like foreign substance
What is X-linked lymphoproliferative syndrome
Inability to eliminate EBV leading to infections mono and development of B cell tumors
What is the mutation in X-linked lymhpoproliferative syndrome
Gene encoding an adaptor molecule called SLAM-associated protein (SAP) that binds to surface molecules involved in activation of NK cells and T and B cells; defects result in susceptibility to viral infection; also cannot form germinal centers (don’t make follicular helper T cells) and don’t produce high affinity abs
What are defects in Th1 responses verses Th17 response associated with
Th1: atypical mycobactterial infections
Th17: chronic mucocutaneous candidiasis and bacterial infections of the skin (Job syndrome)
What is Wiskott-Aldrich syndrome
X-linked dz characterized by thrombocytopenia, eczema, and vulnerability to recurrent infection resulting in early death; thymus is normal, but there is progressive loss of T cells in blood and T zones of LN; do not make abs to polysacch ags and response to protein is low; IgM low, IgG normal; IgA and E elevated; prone to B cell lymphoma
What mutation causes Wiskott-Aldrich syndrome
Gene encoding Wiskott-Aldrich syndrome protein (WASP) located at Xp11.23; linked membrane receptors to cytoskeleton; involved in cell migration and signal transduction
What is the treatment for Wiskott-Aldrich syndrome
HSC transplant
What is ataxia telangiectasia
AR disorder characterized by abnormal gait, vascular malformations (telangiectasia), Neuro deficits, increased incidence of tumors and immunodeficiency
What is the mutation involved in ataxia telangiectasia
Chromosome 11 - encodes ATM (ataxia telangiectasia mutated) that is related to PI-3 kinase; senses DNA damage and activated p53 by phosphorylation; generation of receptors may be abnormal because can’t repair damaged DNA
What are causes of secondary immunodeficiencies
HIV
Irradiation and chemo: decreased BM precursors for all leukocytes
Involvement of BM by cancer: reduced site of leukocyte development
Malnutrition: metabolic deragnements inhibit maturation and function
Removal of spleen: decreased phagocytosis of microbes
Which groups are at risk for development of AIDS
MSM, IV drug abusers, hemophiliacs, recipients of blood and blood components, heterosexual contacts of other high risk groups, Newborn
What are the three major routes of transmission of HIV
Sexual contact, parent real inoculation, passage of virus from infected mothers to their newborn
What are the two ways viral transmission of HIV can occur through sexual transmission
- direct inoculation into bv injured by trauma
- infection of dendritic cells or CD4 cells within the mucosa
Which additional STDs enhance the sexual transmission of HIV
Herpes, chancroid, and syphilis; gonorrhea and chlamydia are also cofactors because of increased inflammatory cells in semen (increase viral load in semen)
What groups of people does parenteral transmission of HIV occur in
Hemophiliacs, IV drug abusers, blood transfusion recipients
How can mothers transmit HIV to their unborn baby
- in utero by transplacental spread
- during delivery through infected birth canal
- after birth by ingestion of breast milk
How has mother to child transmission been controlled in the US
Administration of antiretroviral therapy to pregnant women
Which types of HIV are linked to AIDs
HIV-1 and 2 (HIV 1 most common in US)
Describe the structure of HIV
Spherical, electron dense core surrounded by lipid envelope derived from host; core contains: p24 (major capsid protein), nucleocapsid protein p7/p9, two copies of viral genomic RNA, and 3 viral enzymes - protease, reverse transcriptase and integrate; viral core surrounded by p17; gp120 and 41 stud the envelop *critical for infection
Which antigen is most frequently used to diagnose HIV
P24
What genes does the HIV-1 RNA genome contain
Gag, pol, env; gag and pol -> precursors to yield mature proteins; also contains accessory genes -> tat, rev, vif, nef, vpr, and vpu(regulate synthesis of infections viral particles)
What are the 3 subgroups of HIV-1
M (major)*most common, O (outlier), and N(neither)
What are the two main targets of HIV
Immune system and CNS
What is the long terminal repeat region needed for
Required for initiation of transcription; bind host TF, binds tat
What is gag processed into
P17 (promotes viral assembly at cell surface), p24 (binds cyclophilin A), p7 (RNA binding protein), p6 (interacts with VPR, terminal. Steps of notion building)
How does HIV infect cells
Uses CD4 as receptor and chemokines as coreceptors (gp120 binds) -> CCR5, CXCR4; R5 strains preferentially infect monocyte/macrophages (M-tropic) and X4 strains infect T cells (T-tropic); R5 typically found in acute infection, then T-tropic accumulates
What is the initial step in infection
Gp120 binds CD4 which leads to a conformational change resulting in formation of new recognition site on gp120 for coreceptors; then binding to coreceptors causes conformational change in gp41 that results in exposure of hydrophobic region (inserts into cell membrane of target cell) -> fusion of viral cell with host cell; virus core then can enter
How can chemokines block HIV infection
Block the receptors so HIV cant bind to coreceptors
Describe the steps of viral replication once HIV is in the host
Reverse transcriptase -> cDNA; in quiescent T cells will remain in linear form, in dividing T cells cDNA circularizes, enters nucleus, and integrates into host genome; can be latent or can be transcribed and form viral particles which bud from the membrane and lead to death of infected cell
What kind of T cells is HIV unable to infect
Naive T cells -> they contain active form of an enzyme called APOBEC3G that introduces mutations in the HIV genome; its a cytidine deaminase that introduces cytosine to uracil mutations in viral DNA; this inhibits further DNA replication; activation of T cells converts the enzyme to an inactive state; HIV also can combat this by producing Vif which binds APOBEC3G
Describe how the completion of a viral life cycle occurs in latently infected cells
If an environment antigen is recognized by these cells, IkB is phosphorylated which allows NF-kB to translocate to the nucleus which can bind to the LTR region of HIV genome; HIV DNA is transcribed which leads to production of virions and lysis of cell
Besides direct killing of cells by HIV, how else are T cells lost
Chronic activation of uninflected cells (responding to HIV or other microbes -> activation-induced cell death); non-cytopathic HIV infection activates inflammasome pathway (pyroptosis); destruction of composition of lymphoid tissues, can infect thymus progenitor cells or accessory cells that secrete cytokines needed for CD4 maturation, fusion of infected cells with in infected cells (form giant cells; usually just X4)
What is unique about HIV infection of macrophages
HIV-1 can infect terminally differentiated, non-dividing macrophages with the help of vpr gene -> allows nuclear targeting of HIV pre-integration complex through the nuclear pore; macrophages resistant to cyotpathic effects (replicate virus but do not bud); act as portal of infection (impt in pathogenesis of dz); can be used to transport to other parts of the body (CNS)
What are the major abnormalities seen in the immune function of AIDS
Lymphopenia, decreased T cell function, polyclonal Bcell activation, altered monocyte or macrophage function (decreased class II HLA expression)
Besides macrophages, what other cell types are important for the invitation and maintenance of HIV infection
Follicular (reservoirs; trap HIV with anti-HIV abs -> infect T cells) and mucosal (infected and transport to LN) dendritic cells; dendritic cells have lectin receptor that directly bind HIV
What causes polyclonal B cell activation in HIV infection
Gp41 can promote Bcell growth and diff; HIV infected macrophages produce IL-6 which stimulates proliferation of B cells; both T dependent and independent ab responses are suppressed; therefore, are susceptible to encapsulated bacteria like S pneumoniae and H. Influenzae
What is special about the HIV-isolates from the brain
Exclusively M-tropic
How does HIV cause neurological symptoms
Caused indirectly by viral products and soluble factors produced by infected microglia -> TNF, IL-1 and ; also NO induced in neuronal cells by gp41 has been implicated
What are the phases of HIV infection
Acute retroviral syndrome, middle chronic phase (asymptomatic), clinical AIDS
Describe the characteristics of the acute phase of HIV infection
Mucosal tissues affected (have large number of T cells), few infected cells detectable in blood, associated with damage to mucosal epithelium, defects in mucosal barrier function; followed by dissemination of virus and development of host immune responses (dendritic cells -> LN); within days after exposure, viral replication can be detected in LN -> viremia; humoral and cell-mediated responses 3-7 wks; HIV specific CD8 cells detected @ same time viral load begins to fall (12 wks)
What is acute retroviral syndrome
Occurs 3-6 weeks after exposure and resolves spontaneously in 2-4 weeks; self-limited acute illness with nonspecific symptoms (sore throat, myalgias, fever, weight loss, fatigue)
What is a useful surrogate marker of HIV disease progression
HIV-1 RNA levels in the blood (measure viremia)
What is the viral set point
At the end of the acute phase, viral load and immune response reach an equilibrium; steady-state viremia; predictor of rate of decline of CD4 cells
When does the CD8 response to HIV peak
9-12 weeks
What occurs during chronic infection
Phase of clinical latency; HIV replication and cell destruction continues in LN and spleen; CD4 cells steadily declines; host defenses begin to wane and HIV RNA levels increase; coreceptor switch is associated with a more rapid decline
Describe the presentation of AIDS
Fever >1 month, fatigue, weight loss, diarrhea, generalized LAD, opportunistic infections, secondary neoplasms, and neurological dz emerge
In the absence of treatment, how long does it take for someone with HIV to develop into AIDS
7-10 years
What happens to those who are rapid progressors of HIV
Chronic phase is telescoped to 2-3 years after infection
What happens to those who are coined long-term nonprogessors
Untreated HIV-1-infected individuals who remain asymptomatic for 10 years or more with stable CD4 counts and low levels of plasma viremia (less than 500)
What are elite controllers
Have undetectable plasma viremia (<50 RNA)
In asymptomatic HIV infected individuals, what is usually the sign of progression to AIDS
Oral candidiasis
What does cytomegalovirus usually affect in persons with AIDS
Retina and GI
What is different about infection with M tuberculosis in comparison to other mycobacterium in AIDS patients
Manifests early in the course of AIDS
What is the major manifestation of cryptococcosis
Meningitis
What does toxoplasma Gondi affect in AIDS patients
CNS
What does JC virus cause in AIDS patients
Affects CNS: causes progressive multifocal leukoencephalopathy
Which cancers are AIDS patients at risk for
Kaposi sarcoma, anal cancer in men, cervical cancer in women, B cell lymphoma
What is a common feature of the tumors of AIDs patients
Caused by oncogenes DNA viruses -> kaposi sarcoma herpesvirus, EBV (B cell lymphoma), HPV (cervical and anal cancer)
What is kaposi sarcoma
Vascular neoplasm; HAART has drastically reduced incidence; characterized by proliferation of spindle-shaped cells that express markers of both endothelial cells and smooth m; chronic inflammation infiltrates; not malignant; linked to rare B cell lymphomas called primary effusion lymphoma and multi centric castelman disease
Is HAART effective against lymphomas in AIDS patients
Has decreased the incidence rate overall, but are still 10 fold more likely than the general population to develop lymphoma.
What are the mechanisms that underlie the increased risk of B cell tumors in AIDS patients
- Unchecked proliferation of B cells infected with oncogenic hyperpesviruses in the setting of profound T cell depletion (T cells required to restrain proliferation of these B cells)
- Germinal center B cell hyperplasia in the setting of early HIV infection: mutations in oncogenes MYC (Burkitt lymphoma) and BCL6 (large B cell lymphoma)
Besides lymphoma, what else can EBV cause in AIDS patients
Oral hairy leukoplakia (white projections on the tongue)
What is the immune reconstitution inflammatory syndrome
Patients with advanced AIDS who are given antiretroviral therapy develop clinical deterioration even with CD4 levels increasing and decreased viral load
What are long term complications of HAART
Lipoatrophy (loss of facial fat), lipoaccumulation (excess fat deposition centrally), elevated lipids, insulin resistance, peripheral neuropathy, premature CV, kidney and liver dz
What is amyloidosis
Associated with inherited and inflammatory disorders in which extracellular deposits of fibrillar proteins and responsible for tissue damage and functional compromise; fibrils formed by misfolded proteins which are normally soluble in folded form -> bind proteoglycans and glycosaminoglycans (notable serum amyloid P component)
What occurs with progressive accumulation of amyloid
Encroaches on and produces pressure atrophy of adjacent cells
How can you distinguish amyloid from other hyaline materials
Congo red stain -> shows green apple areas
What are the common forms of amyloid
- AL (amyloid light chain): made up of complete Ig light chains, the aminotermial fragments of light chains, or both; most lambda chains; made from plasma cells; associated with plasma cell tumors
- AA (amyloid associated): derived from liver (non Ig); derived from serum amyloid-associated protein (bound to HDL); assoc with chronic inflammation *secondary amyloidosis
- beta amyloid: core of cerebral plaques in Alzheimer’s; derived from amyloid precursor protein
What are other proteins that can deposit as amyloid
- Transthyretin (TTR): normal serum protein that binds and transports thyroxine and retinol; mutant forms deposit in disorders called familial amyloid polyneuropathies; Normal ttr is also deposited in heart of aged individuals (senile systemic amyloidosis)
- beta2 microglobulin: component of MHC I molecules; identified in patients on long term dialysis
- prion dz
What is the difference between primary and secondary amyloidosis
Primary: associated with plasma cell disorder
Secondary: occurs as complication of chronic inflammatory dz
What is the most common form of amyloidosis
Plasma cell disorders; caused by clonal proliferation of plasma cells that synthesize an Ig prone to form amyloid; ie: patients with multiple myeloma (secrete Ig and Bence-Jones proteins)
What is reactive systemic amyloidosis
Systemic; composed of AA protein; secondary amyloidosis; complicates RA, ankylosing spondylitis and IBD; heroin abusers also at risk; also occur with renal cell carcinoma and Hodgkin lymphoma; SAA produced an enzyme defect prevents its breakdown
What is heredofamilial amyloidosis
- AR called familial Mediterranean fever; autoinflammtory syndrome (excessive production of IL-1); attacks of fever accompanied by inflammation of serosal surfaces; gene encodes pyrin; largely in Armenian, Sephardic Jewish, and Arabic origins; amyloid fibril made up of AA proteins
- AD: deposition of amyloid in peripheral and autonomic nerves; made up of mutant TTRs
Mutations of the TTR gene is seen most often in which populations
Black; increased risk of cardiomyopathy due to amyloidosis
What organs are usually effected with primary vs secondary amyloidosis
Primary: heart, GI, resp, peripheral nerves, skin tongue
Secondary: kidneys, liver, spleen, LN, adrenals, thyroid
What is the macroscopic appearance of amyloidosis
Organ is enlarged and appears gray and waxy
What is seen histologically in amyloidosis
Amyloid deposition is extracellularly and begins between cells; can then encroach on the cells and destroys them; green color (seen under polarized light) caused by crossed beta pleated configuration
What organ is most commonly effected by amyloidosis
Kidney
What are clinical features of amyloidosis
At first: non specific (light headed, syncope, weight loss, weakness);
Renal involvement -> proteinuria (can become nephrotic syndrome); renal failure common cause of death
CHF can occur; restrictive cardiomyopathy
Do amyloid deposits invoke an inflammatory response
No
What are the categories of genetic diseases
- disorders related to mutations in single genes with large effects; highly penetrant (those with mutation is associated with the dz in a large proportion) -> follow classic Mendelian pattern of inheritance
- chromosomal disorders: high penetrance
- complex multigenic disorders: more common; caused by interactions btw multiple variant forms of genes and environmental factors; no single susceptibility gene is sufficient to produce dz; only when several polymorphisms present (multigenic or polygenic); *low penetrance Ie: DM, HTN, autoimmune dz
What are missense mutations
Single nucleotide replacement that causes a different amino acid to be sequenced; if substituted AA is similar to original AA, called conservative
What is an example of nonconservative missense mutation
Sickle mutation; CTC (GAG in mRNA) (glutamic acid) is changed to CAC (GUG in mRNA) (valine)
What is an example of a nonsense mutation
Point mutation in beta globin; CAG replaced with UAG (stop codon); short peptide is degraded -> beta thalassemia
What is the effect of a deletion/insertion of a multiple of 3
Reading frame in tact -> an abnormal protein lacking or gaining one or more AA synthesized
What is the effect of a deletion/insertion of a non-multiple of 3
Frameshift mutation -> incorporation of a variable number of incorrect aa with premature stop codon
Which dz has a 3 base deletion
CF; results in lack of aa 508 (phe)
What sequence is repeated in fragile X syndrome
CGG within the gene called familial mental retardation 1 (FMR1)
What is a unique characteristic of trinucleotide-repeat mutations
They are dynamic, meaning the degree of amplification increases during gametogenesis
What are single-gene disorders with no classic patterns of inheritance
Includes disorders resulting from triplet repeat mutations, mutations in mitochondrial DNA, and those in which transmission is affected by genomic imprinting or gonadal mosaicism
What is an example of a frameshift mutation
- Four-base insertion in hexosaminidase A gene -> causes tay Sachs dz in ashkenazi Jews
- Single base deletion in ABO locus leading to O allele
What is the difference between individuals homozygous and heterozygous for sickle cell
Homo: disorder is always fully expressed
Hetero: only some are HbS and therefore red cell sickling only occurs under unusual circumstances (exposure to low oxygen) -> called sickle cell trait
What is pleiotropism
Same mutant gene may lead to many end effects (sickle cell example) -> sickle cell leads to logjam in difft organs
What is genetic heterogeneity
Same trait may be produced via mutations in different loci; Ie: childhood deafness
What inheritance pattern do single gene disorders follow
AR, AD, X linked
What are characteristics of AD disorders
- generally, one affected parent
- some proportion of patients do not have affected parents -> caused by new mutation; siblings not affected or at risk ; seems to occur in older fathers
- can have incomplete penetrance (have gene but are phenotypically normal)
- age of onset can be delayed (ie: Huntington’s)
What is variable expressivity
A trait is seen in all individuals carrying the mutant gene but is expressed differently; ie: neurofibrotosis type 1
What is dominant negative
When a mutant allele impairs the function of a normal allele; ie: collagen formation
Gain of function mutations are almost always inherited in a _______
AD pattern
What are the characteristics of AR disorders
Parents usually not affected, siblings have 25% chance (recurrence risk for each birth), if mutant gene occurs with a low frequency in population, likely the affected individual is product of a consanguineous marriage
What distinguishes AR from AD disorders
Complete penetrance, onset early in life, new mutations rarely occur, but are not detected (they would be heterozygote), many of mutated genes encode enzymes (in heterozygotes have half normal and half defective)
What are examples of AD disorders
Neuro: Huntington’s, neurofibromatosis, myotonic dystrophy, tuberous sclerosis
Urinary: polycystic kidney dz
GI: familial polyps is cold
Hematopoietic: Hereditary spherocytosis, vW dz
Skeletal: Marfan, enhlers danlos, OI, achondroplasia
Metabolic: familial hypercholesterolemia, acute intermittent prophyria
What are examples of AR disorders
Metabolic: CF, PKU, galactosemia, homocytinuria, lysosomal storage dz, alpha antitrypsin, Wilson, hemochromatosis, glycogen storage dz
Hematopoietic: sickle cell, thalassemia
Skeletal: enhlers danlos, alkaptonuria
Endo: conventional adrenal hyperplasia
Nervous: neurogenic muscular atrophied, fried rich ataxia, spinal muscular atrophy
X-linked disorders are almost always _______
Recessive
Why is there no Y-linked inheritance
Men with Y mutations are usually infertile
What inheritance pattern does glucose-6P DH have
X-linked; predisposes to hemolysis in patients receiving certain types of drugs; heterozygous female can show trait because some RBCs can have the normal allele inactivated
What is an example of X-linked dominant disorder
Vitamin D resistant rickets
What are examples of X-linked recessive disorders
MSK: duchenne MD
Blood: hemophilia, chronic granulomatous dz, glucose 6PDH
Immune: agammaglobulinemia, wiskott-Aldrich
Metabolic: diabetes insipidus, lesch-nyhan syndrome
NErvous: Fragile X syndrome
What is affected in AD disorders
NOT enzymes -> structural proteins and receptors
What can a lack of tyrosinase cause
Lack of melanin production
What is the difference between hemoglobinopathies and thalassemia
Hemoglobinopathies: defects in structure of glowing
Thalassemias: mutations that affect amount of globin chains synthesized
What drug causes an adverse reaction in people with G6PD deficiency
Antimalarial drug, primaquine -> causes severe hemolytic anemia
What parts of the body does Marfan syndrome mostly affect
Eyes, skeleton, CV
How does the mutation in fibrillin cause the effects of Marfan syndrome
- loss of structural support in microfibril rich connective tissue
- excess activation of TGF beta signaling
Mutations in what causes Marfan
FBN1 (FBN2 -> congenital contractural arachnodactyly); most are missense mutations; inhibits polymerization of fibrillin fibers (dominant negative effect); reduction of fibrillin below a certain threshold weakens tissue (haploinsufficiency))
What problems does excess production of TGF beta in Marfans cause
Bone overgrowth and myxoid changes in mitral valves; normal microfibrils sequester TGF beta; MMPs are also activated causing further breakdown of ECM
What is dolichocephalic
Long-headed; *marfans
What are skeletal abnormalities seen in marfans
Tall, flexible, bossing front eminence, prominent supraorbital ridges, kyphosis, scoliosis, or rotation/slipping of lumbar vertebrae; chest is either pectus excavatum or carnatum
What are the ocular presentations of marfans
Bilateral subluxation or dislocation (outward and upward) of the lens (ectopia lentis); *very uncommon in any other dz
What CV issues are seen in marfans
Mitral regurgitation, elongation of chordae tendinae, aortic dissection, mitral valve prolapse
What is required for diagnosis of marfans
Involvement of 2 of 4 organ systems (skeletal, CV, ocular and skin) and minor involvement of another organ
How do you treat marfans
Beta blockers (decrease aortic wall stress)
Which 2 types of ehlers danlos are AR
kyphosclosis (VI) -> defect in lysyl hydroxylase
Dermatosparaxis (VIIc) -> defect in procollagen peptidase
* the rest are AD
What internal complications can occur in ehlers danlos
Rupture of colon and large arteries (vascular), ocular fragility with rupture of cornea and retinal detachment (kyphoscoliosis), and diaphragmatic hernia (classic)
What causes the vascular type of ehlers danlos
Abnormalities of type III collagen (COL3A1 gene); heterogenous because 3 distinct mutations can cause this variant; some affect rate of synthesis of pro alpha chains, some affect secretion of type III proollagen, and some lead to structural abnormalities
Which type of EDS results from a defect in the conversion of type I procollagen to collagen
Arthrochalasia and dermatosparaxis; this step involves cleavage of. Noncollagen peptides at N and C terminus of procollagen via peptidases; defect in arthrochalasia type -> mutations in COL1A1/2; leads to formation of pro alpha 1/2 chains that resist cleavage; dermatosparaxis type -> mutation of procollagen N peptidase gene
What mutations cause classic type EDS
Genes for type V collagen (COL5A1/2)
What does a mutation of tenascin-X cause
EDS-like syndreom; affects synthesis and fibril formation of type VI and I collagen
Describe the process of cholesterol metabolism/transport
Leaves the liver via VLDLs (rich in TAGs, low cholesterol esters) -> blood -> cleaved by LPL to IDL (low TAG, high cholesterol esters; has apo B-100 and E) -> can be taken up by liver by receptor mediated transport via LDL receptor and recycled to VLDL OR converted to LDL (removes TAGs and apo E)
What is the immediate and major source of plasma LDL
IDL
What does the exit of cholesterol from the lysosomes require
NPC1/2; released to cytoplasm for membrane synthesis; this suppresses cholesterol synthesis within the cell by inhibiting 3-hydroxy-3-methyglutaryl coenzyme A (HMG CoA) reductase, activates acyl-coenzyme A (favors storage of excess cholesterol), and suppresses synthesis of LDL receptors (protects from excessive uptake)
What is impaired in familial hypercholesterolemia
LDL receptor: cant uptake LDL OR IDL; causes accumulation of LDL and excess production of LDL
What kind of receptors do macrophages contain for LDL
Scavenger receptors -> receptor for chemically. Altered LDL; increased transport in hypercholesterolemia; responsible for presence of xanthomas and atherosclerosis
What are the groups of mutations found in familial hypercholesterolemia
Class I: uncommon; complete failure of synthesis of receptor protein
Class II: common; encode receptor proteins that accumulate in ER b/c misfolded
Class III: affect LDL binding domain of receptor
Class IV: bind LDL normally, but fail to localize in coated pits and LDL not internalized
Class V: pH-dependent dissociation of receptor and bound LDL fails to occur; trapped in endosome and fail to recycle
What do statins do
Inhibit HMG CoA and thus lead to increased synthesis of LDL receptors
What is primary accumulation (in lysosomes)
Catabolism of substrate is incomplete; accumulation of partially degraded material
What is secondary accumulation (in lysosomes)
Impaired autophagic; accumulation of autophagic substrates such as polyubiquinated proteins and old mitochondria -> can cause generation of ROS and apoptosis
How are lysosomal storage diseases treated
Enzyme replacement therapy; substrate reduction therapy (reduce the production of the substrate that cant be broken down), exogenous competitive inhibitor of the enzyme can bind to mutant enzyme and act as folding template that assists proper folding and prevent its degredation (called molecular chaperone therapy)
Which organs are generally enlarged with lysosomal storage disorders
Spleen and liver; contain many macrophages which are very rich in lysosomes
What are GM2 gangliosidoses
Group of 3 lysosomal storage diseases caused by inability to catabolism GM2 gangliosides; requires 3 polypeptides encoded by 3 genes
What is tay Sachs disease
Most common form of GM2 gangliosidosis; results from mutation in alpha subunit locus on chrom 15 that causes severe deficiency of hexosaminidase A; prevalent among Ashkenazic Jews; infants normal at birth, manifest symptoms at 6 mo; motor and mental deterioration, muscular flaccidity, blindness, dementia, cherry red spot in macula, 1-2 yrs -> vegetative state, death at 2-3 years; unfolded protein response -> possible chaperone therapy
What tissues are most affected in tay Sachs
Neurons in central and autonomic NS, retina; (though GM2 accumulates in many tissues); neurons are ballooned w/cytoplasmic vacuoles; stains for fat are positive; destruction of neurons, proliferation of microglia, accumulation of lipids in phagocytes of brain; ganglion cells in retina swollen
What are the GM gangliosidosis examples of
Sphingolipodoses
What kind of disease are Neimann pick type A and B
Sulfatidoses
What is the deficiency in Niemann pick diseases
Sphingomyelinase; type A: sever in infantile, Neuro impairment, visceral accumulations of sphingomyelin, wasting and early death; type B: organomegaly but no CNS involvement; survive into adulthood *common in Ashkenazi Jews; gene expressed on maternal chromosome as a result of epi genetic silencing of paternal gene (usually AR but those who inherit mutant allele from mom can get dz)
What kind of mutation causes type A niemann pick dz
Missense mutation -> complete deficiency of sphingomyelinase; causes foaminess of cytoplasm; stain for fat; lipid-laden foam cells widely distributed in spleen, liver, LN, BM, tonsils, GI, and lung;
What are the clinical features of niemann pick type A
splenomegaly but not hepatomegaly; in brain, gyri shrunken and sulci widened; retinal cherry spot seen; protruberant abdomen; symptoms start at 6 mo -> followed by failure to thrive, vomiting, fever, generalized LAD, and deterioration of psychomotor function; feat within 1-2 years
What causes niemann pick type C
Mutation in NPC1/2 (1 more common); causes primary defect in non-enzymatic lipid transport; NPC1 is membrane bound - NPC2 is soluble; both transport free cholesterol from lysosomes to cytoplasm; heterogenous; may present as hydros fetalis and stillbirth, neonatal hepatitis, or chronic characterized by progressive Neuro damage (most common) *ataxia, vertical supranuclear gaze palsy, dystonia, dysarthria, psychomotor regression
What is gaucher disease
Sulfatidose class; cluster of AR disorders resulting from mutations in gene encoding for glucocerebrosidase (normally cleaves glucose residue from ceramide) *most common lysosomal storage disorder; glucocerebroside accumulate in phagocytes (Formed from catabolism of glycolipids from membranes of senescent leukocytes and RBCs)
What causes the pathological presentation of Gaucher disease
Not just by burden of storage material: also by activation of macrophages and secretion of IL-1,6, and TNF
What are the subtypes of Gaucher
- Type I: most common, chronic nonneuronopathic form; storage of glucocerebrosides limited to phagocytes throughout body, but not brain; *splenic and skeletal involvemtns; Jews; reduced levels of enzyme activity; longevity shortened slightly
- Type II: acute neuronopathic; infantile acute cerebral pattern; no enzyme activity; hepatosplenomegaly; dominated by CNS involvement; early death
- Type III: intermediate; systemic involvement of t yep I, but also have CNS involvement beginning in early adulthood
Where are the gaucher cells found
spleen, liver, BM, tonsils, peyers patches, thymus, LN
What is the difference between the histology of gaucher cells compared to other lysosomal storage diseases
Don’t appear vacuolated, but instead have a fibrillar type of cytoplasm (like crumpled tissue paper); have one or more dark eccentrically placed nuclei
What does accumulation of gaucher cells in the bone marrow cause
Type I** causes bone erosion
How does neuronal damage occur in gaucher disease
No lipid accumulation in neurons -> cytokines released from neighboring phagocytes damage neurons; gaucher cells seen in virchow Robbins spaces
Describe clinical features of each type of gaucher disease
Type I: symptoms appear in adult; splenomegaly (thrombocytopenia and pancytopenia secondary), bone pain,
Type II and III: convulsions, progressive mental deterioration, liver, spleen, LN also affected
What is the treatment for gaucher
Recombinant enzyme replacement therapy; HSC transplant (defect resides in mononuclear phagocyte cells originating from marrow)
What are mucopolysaccharidoses
Group of syndromes resulting from deficiencies of enzymes involved in degredation for of mucopolysaccharides (glycosaminoglycans)
What accumulates in MPS
Dermatomes sulfate, heparan sulfate, keratan sulfate, and chondroitin sulfate
What is the inheritance pattern of MPSs
All are AR except Hunter syndrome which is X-linked recessive
What are the features of MPSs
Coarse facial features, clouding of cornea, joint stiffness, mental retardation, urinary excretion of accumulated mucopolysaccharides; hepatosplenomegaly, skeletal deformities, valvular lesions, subendothelial arterial deposits, lesions in the brain
Where are the accumulated MPS found in MPSs
Phagocytic cells, endothelial cells, smooth m cells and fibroblasts; sites of involvement are spleen, LN, liver, BM, bv and heart
Which two disease show “zebra bodies” on EM
Niemann pick and MPSs
What is Hurler syndrome
MPS I: deficiency of alpha 1 iduronidase; most severe; affected children normal at birth, develop HSM by age 6-24 mo, growth is retarded, coarse facial features, skeletal deformities, death by age 6-10 due to CV complications
What is HUnter syndrome
MPS II: absence of corneal clouding, milder clinical course
Describe glycogen synthesis
Glucose converted to glucose 6 p via hexokinase; glucose6P-> G1P via phosphogluctomutase -> uridine diphosphoglucose -> polymer built to form glucose molecules linked by alpha 1,4 bonds
How does glycogen degredation occur
Enzymes break off G1P until 4 glucose residues remain leaving a branched oligosaccharide called limit dextrin; can be further degraded by debranching enzyme; *also degraded in lysosomes by acid Maltase
What are the 3 subgroups of glycogensoses
Hepatic forms, myopathic forms, and form associated with deficiency of acid maltase or lack of branching enzyme
Describe the hepatic forms of glycogenoses
Ie: deficiency of glucose 6 phosphatase (von gierks; type I): form of hepatic hypoglycemic glycogen storage disease; hepatic enlargement and hypoglycemia dominate in any of these disorders; renomegaly also seen; hyperlipidemia; bleeding tendency
Describe the myopathic forms of glycogen storage diseases
In skeletal mm, glycogen used as source of energy during activity; ATP generated by glycolysis which leads to production of lactate; if enzymes that fuel this pathway are deficient, muscular weakness occurs; ex: deficiency of muscular phosphorylase (McArdles: type V) or muscle PFK (type VII); present with m cramps after exercise and low lactate levels after exercise; serum creatinine kinase elevated
What are glycogen disorders associated with deficiency of acid maltase (alpha glucosidase) and branching enzyme linked to
Associated with glycogen storage in many organs and death early in life; acid maltase -> type II (Pompe) *cardiomegaly most prominent feature
What inheritance pattern do most familial cancers have
AD
What is the procedure used to examine chromosomes
Stop dividing cells in metaphase with mitotic spindle inhibitors (cycle is) and then stain the chromosomes
What is the shorthand used in karyotyping
Total # of chromosomes, sex chromosome complement, description of abnormalities in ascending numerical order; ie: male with trisomy 21: 47, XY, +21
What are the causes of aneuploidy
Nondisjunction (either have extra or one less chromosome) -> results in trisomy or monosomy and anaphase lag (one homologous chromosome in meiosis or one chromatid in mitosis lags and is left out of the cell nucleus) -> results in one normal cell and one will monosomy
Are monosomies of autosomes usually compatible with life
No
What is an example of mosaicism
Turner sydrome; have combination of cells that are 45,X and 47, XXX
What is a ring chromosome
Special kind of deletion; produced when break occurs at both ends of a chromosome with fusion of the damaged ends (46,XY,r(14)); usually results in serious consequences
What is an inversion
Two breaks within single chromosome and reinsertion of the inverted intervening segment; when it involves only one arm -> paracentric; if breaks are on opposite sides of centromere -> pericentric; fully compatible with normal development
What is an isochromosome
Results when one arm is lost and the remaining arm is duplicated; identical information in both arms; most common in live births is long arm of the X -> i(X)(q10); associated with monosomy for genes on short arm of X and trisomy on long arm of X
What is translocation
Segment of one chromosome is transferred to another; balanced reciprocal translocation -> single breaks in 2 chromosomes which exchange material (normal but at increased risk for producing abnormal gametes); robertsonian (centric fusion) -> translocation btw 2 acrocentric chromosomes (breaks close to centromere); produces one long and one short chrom (small usually lost) -> normal but can lead to abnormal progeny
Where does the meiotic nondisjuction that causes Down syndrome most likely occur
In ovum -> correlation with mothers age
In the remaining cases not caused by nondisjunction, how does Down syndrome occur
- Robertsonian translocation of long arm of 21 to another acrocentric chromosome; cases are commonly familial
- also could be mosaics -> mixture of cells with 46 and 47 chromosomes; results from mitotic nondisjunction of chrom 21 during embryogenesis; milder depending on proportion of normal cells
- in both of these cases, maternal age serves no importance
What are the diagnostic features of downs
Flat face, oblique palpebral fissures, epicanthic folds *evident at birth
What are the clinical features of downs
- Congenital heart disease: Latium primum, atrial septal defects, AV valve malformations, ventricular septal defects
- atresia of esophagus and small bowel
- increased risk of developing acute leukemia: acute megakaryoblastic leukemia
- older than 40 -> develop neuropathologist changes characteristic of Alzheimer’s
- abnormal immune responses that predispose them to serious infections, particularly of the lungs and thyroid autoimmunity
- intestinal stenosis, gap btw first and second toe, hypotonia, umbilical hernia, simian crease, abundant neck skin
What genes are though to be involved in downs
Those involved in mitochondrial energy pathways, folate metabolism, and CNS development; thought to be overexpression of genes
What is trisomy 18
Edwards syndrome: trisomy and mosaic type; prominent occiput, mental retardation, micrognathia, low set ears, short neck, overlapping fingers, congenital heart defects, Renal malformations, limited hip abduction; rarely survivable past 1st year
What is trisomy 13
Patau syndrome: trisomy, translocation, and mosaic type; renal defects, rocker-bottom feet, cleft lip and palate, microcephaly and mental retardation, microphthlamia, polydactyly, cardiac defects, umbilical hernia; not survivable past 1st year of life
What are the two disorders related to chrom 22q11.2 deletion syndrome
DiGeorge and velocardiofacial syndrome
What are the clinical features of velocardiofacial syndrome
Facial dysmorphism (prominent nose, retrognathia), cleft palate, CV anomalies, and learning disabilities
What are individuals with 22q11.2 deletion at risk for
Psychotic illnesses: schizophrenia, bipolar
ADHD also seen
What gene is considered to be affected by the 22q11.2 deletion
TBX1: T box TF
What are the cytogenic disorders involving autosomes
Downs, digeorge, velocardiofacial
What allows sex chromosomes to be more tolerable of cytogenic disorders
Lyonization of X chromosome and modest amount of genetic material carried by Y chromosome
Where is the SRY gene located
Short arm of Y chromosome
What are all Y chromosome deletions associated with
Azoospermia
What is Klinefelter syndrome
Male hypogonadism that occurs when there are two or more X chromosomes and one or more Y chromosomes; rarely diagnosed before puberty; increase in length btw soles and the pubic bone (appearance of elongated body), eunuchoid body habit is w/long legs, small atrophic testes and small penis; lack of secondary sex characteristics (deep voice, hair), gynecomastia, mean IQ lower, but not mental retardation
What are individuals with Klinefelter syndrome at risk of developing
T2DM; mitral valve prolapse; osteoporosis and fractures due to sex hormonal imbalance; *breast cancer, extragonadal germ cell tumors, and autoimmune dz
What is the only consistent finding in Klinefelter syndrome
Hypogonadism
What are the hormone levels of someone with Klinefelter syndrome like
High FSH, low testosterone; high estradiol
Besides hypogonadism what happens to other sexual organs in someone with klinefelter
Testicular tubules can be atrophied and replaced by pink, hyaline, collagenous ghosts, leydig cells appear prominent
What is the classic karyotype of someone with klinefelter
47,XXY; results from nondisjunction of either parent
Why do klinefelter patients still have hypogonadism if one X chromosome is inactivated
Genes that escape lyonization
-also, in this syndrome, X chromosome with shorter CAG repeat is inactivated therefore they are less sensitive to androgens (longer CAG repeats encode for testosterone receptors that are less sensitive)
What are the kinds of karyotypic abnormalities seen in Turner syndrome
45,X: either missing chromosome, abnormalities of X chromosome or mosaics
What are the structural abnormalities of the X chromosome seen in Turner syndrome
- most common: isochromosome of the long arm 46,X,i(X)(q10) resulting in loss of short arm
- deletion of portions of both long and short arms -> ring chromosome 46,X,r(X)
- deletion of portions of short or long arm 46X,del(Xq) or Xp
What are the karyotypes mosaic turner patients may have
- 45,X/46,XX
- 45,X/46XY
- 45,X/47,XXX
- 45,X/46,X,i(X)(q10)
What are turner patients who have Y chromosomes at risk for
Gonadal tumor (gonadoblastoma)
What is the presentation in infancy of turners patients
Swelling of dorsum of hand and foot. Due to lymph stasis and swelling of the nape of the neck (distended lymph channels producing cystic hygroma); swellings subside but leave b/l neck webbing and looseness of skin on the back of neck
What are common clinical features of turner syndreom
Congenital heart disease; left sided CV abnormalities (preductal. Coarctation of aorta and bicuspid aortic valve) *most impt cause of increased mortality; pigmented neck, broad chest, cubitus valgus
-at puberty, don’t develop secondary sexy characteristics, short stature, amenorrhea (last two establish diagnosis) *turner sydrome most impt cause of primary amennorhea; can also develop hypothyroidism and glucose intolerance, obesity, and insulin resistance
Why is the insulin resistance seen in turners syndrome important?
Growth hormone is often used to treat these patients, but this would worsen insulin resistance
Is it believed that the defect in turners syndrome is inherited from mom or dad
Dad; problem with gametogenesis
What is significant about the ovaries of turner patients
Develop normally in early embryogenesis, but because lack one X chromosome, begin to deplete rapidly and complete loss by age 2; menopause occurs before menarche (streak ovaries)
What genes are involved in Turner syndrome phenotype
Short stature homeobox (SHOX) -> active in both chromosomes
What are the different types to classify gender
Genetic sex: presence or absence of Y chromosome
GOnadal: histological characteristic of gonads
Ductal: presence of derivatives of mullerian or wolffian ducts
Phenotypic or genital: appearance of external genitalia
What is the difference between a true hermaphrodite and a pseudohermaphrodite
Hermaphrodite is presence of both ovarian and testicular tissue; pseudo is disagreement between gonadal and phenotypic sex
What does the expansion of trinucleotide repeat mutations depend on
Sex of transmitting parent; in fragile X -> occurs during oogenesis, in Huntington’s occurs during spermatogenesis
What are the mechanisms by which trinucleotide repeat mutations can cause disease
- loss of function (fragile X); repeats occur in noncoding regions
- toxic gain of function (Huntington and spineocerebellar ataxia); repeats occur in coding regions
- toxic gain of function mediated by mRNA (fragile X tremor-ataxia syndrome); noncoding parts affected
What repeats are usually seen in coding regions
CAG -> codes for polyglutamine tracts; characterized by neurodegeneration, typically striking in midlife; abnormal protein impairs function of normal (dominant negative) or acquire new pathophysiologic toxic activity; proteins can also aggregate and cause ER stress response *morphologic hallmark = accumulation of aggregated mutant proteins in large intranuclear inclusions
Where is the mutation located for fragile x syndrome
Familial mental retardation 1 (FMR1)
What are the clinical features of fragile x sydrome
Males: mentally retarded, long face with large mandible, large everted ears and large testicles (macro-orchidism), hyperextensible joints, high arched palate, mitral valve prolapse *affects males most
What are some abnormalities seen with the inheritance partner of fragile X
- males can be carriers: have the gene but are not affected; referred to as normal transmitting males
- females are affected
- risk depends on position in pedigree (brothers have less risk than of grandsons)
- anticipation: observation that clinical features worsen with each successive generation
What triplet is seen in fridreich ataxia
GAA in the intron; causes loss of protein function
What is the triplet in fragile X syndrome
CGG
What are premutations
Small repeats (55-200 CGG repeats) in normal trasmitting males and carrier females
How do premutations expand to full mutations
When inherited by carrier male -> doesn’t really transform; when inherited by carrier females, high probability of dramatic amplification *during process of oogenesis, premutations converted to mutations by triple amplification; explains unusual inheritance pattern
How does mental retardation occur as a result of fragile X syndrome
Repeats in UTR of FMR1 gene causes DNA methylation resulting in transcriptional silencing; FMRP not made; FMRP most abundant in brain and testis
What are the functions of FMRP
- Selectively bind mRNAs associated with polysomes and regulates their intracellular transport to dendrites; it binds to mRNAs that encode for proteins that regulate synaptic function
- translation regulator: at synapses, FMRP suppresses protein synthesis from bound mRNAs in response to signaling through group I metabotropic glutamate receptors; thus, reduction in FMRP results in translation of these mRNAs which changes function of synapses
What is the method used to diagnose fragile X
PCR detection of repeats
What is fragile X tremor/ataxia
CGG premutations in FMR1 that cause a diseases; causes premature ovarian failure (before age 40), transmitting males exhibit progressive neurodegenerative syndrome starting in 6th decade, intention tremors and cerebellar ataxia (can progress to Parkinson’s); FMR1 gene is transcribed instead of methylated -> accumulate in nucleus and form inclusions -> recruit RNA binding proteins
What are characteristic of mitochondrial disorders
- exert effects mostly on CNS, skeletal m, cardiac m, liver, and kidneys
- heteroplasmy: each mit contains thousands of copies of mtDNA and thus mutations can affect some but not all of copies; tissues can harbor both wild type and mutant; minimum # of mutant but appear before causing oxidative dysfunction that gives rise to disease (Threshold effect)
What is an example of mitochondrial disorders
Lender hereditary optic neuropathy: neurodegenerative disease, manifests as progressive b/l loss of central vision; first noted between ages 15-35; leads to blindness
What is maternal/paternal imprinting
Maternal: maternal allele is silenced and vice versus
Where does imprinting occur
In ovum or spleen before fertilization
What are the mechanisms of imprinting
DNA methylation at CG nucleotides, histone H4 deacetylation and methylation
What is Prader-Willi syndrome
Characterized by mental retardation, short stature, hypotonia, profound hyperplasia, obesity, small hands and feet, and hypogonadism; caused by deletion of band q12 in long arm of chromosome 15 of the paternally derived chromosome
What is angelman syndrome
Deletion of q12 on chromosome 15 of the maternal chromosome; mentally retarded, ataxic gait, seizures, inappropriate laughter (happy puppets)
What is the significance of unilateral disomy in angelman/prader will I
Patients with prader Willi without the deletion have shown two maternal copies of chromosome 15 (Does not have set of non-imprinted genes so has dz); angelman syndrome without deletion -> have two sets of paternal chromosome 15
What gene is affected in angelman syndrome
Ubiquitin ligase (UBE3A)
What gene is involved in prader-willi
No single gene; SNORP family (encodes small nucleolar RNAs involves in modifications of ribosomal RNAs) -> loss of SNORP function
What is unique about the inheritance pattern of osteogenesis imperfecta
AD, but more than one child is often affected; gonadal mosaicism thought to be responsible -> mutation occurs postzygotically during early embryonic development (germ cells have defect but somatic cells don’t; can then transmit to children)
What is the difference between constitutional and somatic genetic markers
Constitutional: present in all cells of the effected individual (CFTR)
Somatic: restricted to specific tissue types (KRAS in cancers)
What are the indications for genetic testing after birth
Multiple congenital anomalies, suspicion of metabolic syndrome, unexplained mental retardation or delay, suspected aneuploidy (features of downs), suspected monogenic disease
What is Sanger sequencing
Amplified DNA mixed with a DNA pol, primer, nucleotides, and four dead end nucleotides labeled with different fluorescent tags; size separation by electrophoresis -> sequence read and compared to normal sequence to detect mutations
What is pyrosequencing
Same set up as Sanger but instead of terminator nucleotides it involves cycling individual nucleuotides one at a time into the reaction; if one or more are incorporated into the strand, pyrophosphatase is released and involved in rx with luciferase that produces light; more sensitive than Sanger; sometimes used for cancer biopsies
Describe fluorescence in situ hybridization
Uses DNA probes that recognize sequences specific to particular chromosome regions; used to detect abnormal chromosome number, subtle microdeletoins, or complex translocations, and gene amplification
What is the importance of multiplex ligation dependent probe amplification
Detect anomalies too big for PCR and too small for FISH; uses pair of probes that hybridizes with DNA; probes create template to be amplified by PCR *CFTR
What is southern blotting used for
Detection of trinucleotide repeats
What is the importance of microarray technology
Can be used to detect genetic anomalies without prior knowledge of the chromosomal regions affected
What is array based comparative genomic hybridization
Test DNA and normal DNA are labeled with 2 diff fluorescent dyes; then cohybridized to array with DNA probes; if two samples equal, all spots will be yellow, if not equal will skew towards red or green
When are SNP arrays used
To uncover copy number abnormalities in pediatric patients when the karyotype is normal but a structural abnormality is still suspected
What are the types of genetic polymorphisms useful for linkage analysis
SNPs and repeat length polymorphisms (mini satellite and micro satellite repeats) -> used for PKD1 in polycystic kidney dz; also used for paternity and criminal investigations
What are genome wide association studies
Used to perform linage studies of complex dz (diabetes, HTN); large cohoes of patients with and without a disease are examined across entire genome for common genetic variants or polymorphisms that are over expressed in pts with dz; also used for height, hair color, etc
Where is DNA usually methylated
CpG islands.
How can DNA methylation be detected
Treat it with sodium bisulfite which converts unmethylated cytosine to uracil; methylated cytokines protected and remain unchanged
