W2P1 Flashcards
Histo of skin Wound healing Hypersensitivity Laboratory Immunology Adaptive Immune deficiences Autoimmunity and tolerance Asthma and Rhinits
What are hypersensitivities
- what do they result in
Exaggerated immune mechanisms directed against innocuous antigens
- Resulting in tissue injury
- Causing many known human diseases
- Can be fatal
What classification system is used for hypersensitivities?
Coombs and Gell classification:
Type I: Immediate hypersensitivity (IgE)
Type II: Antibody-dependent cell mediated cytotoxicity (ADCC) (IgG, IgM)
Type III: Immune complex mediated (IgM, IgG)
Type IV: Delayed type (T cell mediated)
Type 1 Hypersensitivity:
Immediate type
most common type. seen in 20% of population
This is an allergic reaction induced by specific antigen/allergen
provoked by RE-EXPOSURE to the same antigen
mediated by IgE antibodies, which activates tissue mast cells to release HISTAMINE [pro-inflammatory] and…. circulating basophiles
to release local or systemic pro-inflammatory mediators
Type 2 Hypersensitivity
- which ABs are involved
- how does it get triggered
Antibody Dependent Cell Mediated Cytotoxicity
- antibodies coating pathogens (usually viruses) are taken up via FcγR111 on NK cells, leading to the killing of the cells the viruses had infected. The viruses must be presented by MHCI.
this involves IgG and IgM produced AGAINST
a. intrinsic Ag (self antigens)
- failure in immune tolerance
- cross reactivity
b. extrinsic Ag absorbed on host cells surface
- i.e. penicillin at the surface of RBC
Once type 2 hypersensitivity antibodies bind to the surface of host cells, what happens?
4 pathways can be initiated by IgG or IgM binding in type 2 hypersensitivity:
Opsonization ( phagocytosis)
Complement activation (MAC, lysis)
NK cell activation (via perforins and Granzymes, by binding to Fc of AB)
Activation or blockage of important cell receptors
One method employed in Type 2 hypersensitivity is the activation or blockage of important cells receptors.
what is an examples of a disease resulting from this specific pathway?
Myastenia gravis
What are examples of type 2 hypersensitivities
ADCC mediated pathologies
AB and Rh blood group incompatibilities (Transfusion reactions)
Autoimmune diseases :
- Idiopathic Thrombocytopenic Purpura
- Myasthenia gravis
- Goodpasture’s
- Graves’
Some drug reactions
Type 3 hypersensitivity
Immune Complex Mediated Hypersensitivity
Caused when Antigen-Antibody complexes form, which happens when there is an antigen excess compared to the amount of antibodies
Immune complexes form in large amounts in the circulation
Deposition in various tissues
Skin
Joints
Kidneys…
caused when soluble antigen-antibody (IgG or IgM) complexes, which are normally removed by macrophages in the spleen and liver, form in large amounts and overwhelm the body These small complexes lodge in the capillaries, pass between the endothelial cells of blood vessels - especially those in the skin, joints, and kidneys - and become trapped on the surrounding basement membrane beneath these cells The antigen/antibody complexes then activate the classical complement pathway
In type 3, activation of the complement pathway may cause:
Lodge in capillaries
Immune complexes activate classical complement pathway
which may cause:
a. massive inflammation, due to complement protein C5a;
b. influx of neutrophils, due to complement protein C5a , resulting in neutrophils discharging their lysosomes and causing tissue destruction and furthers inflammation
c. MAC lysis of surrounding tissue cells, due to the membrane attack complex, C5b6789n; and
d. aggregation of platelets, resulting in more inflammation and the formation of microthrombi that block capillaries
Type 3 examples
Serum sickness Immune Complex Glomerulonephritis Hypersensitivity pneumonitis Extrinsic Allergic Alveolitis (Farmer’s lung) SLE Arthritis?
What is Serum Sickness
(systemic reaction):
In the pre-antibiotic era, antiserum made by immunizing horses used to treat pneumococcal pneumonia
If a course needed, in some individuals, would lead to a systemic type III hypersensitivity reaction on first exposure
7–10 days after the injection of the horse serum
chills, fever, rash, arthritis, sometimes glomerulonephritis
- self limiting disease
after a second dose of antigen, it would follow the kinetics of secondary antibody response and the onset of disease occurs typically within a day or two
What are some manifestations that are present when the ration of antigens is greater than the ratio of antibodies
antigen:antibody COMPLEXES
lead to:
Fever
Vasculitis
Arthritis
Nephritis
Example of a type 4 hypersensitivity test
Delayed type Hypersensitivity
T- cell mediated
- i.e. Tuberculin test (PPD), used to determine previous exposure by exposing pt to PPD, eliciting a T4 reaction if patient is positive (2nd exposure)
Purified Proteine Derivative
Small amounts of tuberculin—a complex mixture of peptides and carbohydrates derived from M. tuberculosis—are injected intradermally. In individuals who have previously been exposed to the bacterium, either by infection with the pathogen or by immunization with BCG, an attenuated form of M. tuberculosis, a local T cell-mediated inflammatory reaction evolves over 24–72 hours
Type 4
Response mediated by TH1 cells
- Recognize complexes of peptide: MHC class II on APCs
- Releasing IFN-γ and TNF-β…
- Stimulating the expression of adhesion molecules on endothelium and increase local blood vessel permeability
Attracting, retaining and activating macrophages
- Allowing plasma and inflammatory cells to enter the site
- Causing swelling (Induration)
- Each phase takes several hours
- Response appears only 24–48H later
What are some examples of type 4 hypersensitivities
Type IV hypersensitivity reaction to poison ivy
Contact dermatitis with poison ivy
- Response to a chemical in the poison ivy leaf
- Caused by direct exposure- first time exposure
- Mediated by T lymphocytes (CD4, CD8)
Can also occur upon exposure to
Other plants Nickel or other metals Medications Rubber Cosmetics Fabrics and clothing Detergents Solvents Adhesives …
IgE
- what are they produced by
- where are they predominantely located?
- What receptor are they tightly bound to
- IgE produced by plasma cells
IgE located predominantly in tissues
IgE tightly bound to FcE expressed at the surface of
- Tissue mast-cells
- Circulating basophils and activated eosinophils
What is the typical sequence of events for Allergic reaction?
Typical sequence of events:
- Re-Exposure to Antigen (Allergen)
- Presentation through APC
- Activation of TH2
- Production of IgE
Role of Histamine
- causes bronchoconstriction = difficulty breathing
- vasodilation and permeability = edema, uriticaria/hives
What are some treatments to type 1 sensitivities
- anti-histamines: to broncho dilate and decrease vascular permeability
- corticosteroids: decrease inflammatory response
- Epi: Intramuscularily in emerg situations during severe attacks. to constrict blood vessels and prevent anaphylactic shock.
Is immediate hypersensitivity symptoms localized or systemic?
IT DEPENDS on:
nature of allergen
route of introduction of allergen
several host factors
What does it mean to be atopic?
denoting a form of allergy in which a hypersensitivity rxn such as dermatitis or asthma may occur in a part of the body not in contact with the allergen
- it is an increased tendency to mount an IgE response to innocuous antigen
- has a strong familial bias
What cytokines are released by TH2 cells?
TH2 are derived from CD4 naive T cells
they release: IL-4, IL-5, IL-13, IL-31
their function: to recruit more immune cells: mast cells, T cells, eosinophils
Initial environmental/hygiene hypothesis vs modified hypothesis
less hygenic environments predisposing you to infections PROTECTS us against ATOPIC diseases
but how? following hypothesis
initial: Infections that evoke TH1 response early in life might REDUCE the likelihood of TH2 response later in life
modified: there has been an increase in incidence of TH2? mediated autoimmune disease
so really what we need is the development of TREG cytokines that result from infections that MIGHT be able to protect use from atopy.
because too high T1/T2 = atopic/autoimmune diseases
What are the three effector mechanisms for an allergic reaction?
Mast cells: histamine, heparin, proteases. They release IL3 and IL4 to continue the stimulation of TH2 cells.
Basophiles
Eosinophils
all of these have the FC receptor for IgE
Epinephrine
Stimulation of:
A1 adrenergic receptor
- increase peripheral vascular resistance by promoting vasoconstriction
- Reduces angioedema
- Improves coronary perfusion
B1 adrenergic receptor
- Increased inotropic and chronotropic effect
B2 adrenergic receptor
- Bronchodilation
- Decrease release of inflammatory mediators from mast cells and basophils
Which method of EPI administration is more affective?
intramuscularly> subcutaneously
recommended location of injection during anaphylaxis: anterolateral aspect of the thigh
Mast Cell
Fundamental role in innate immunity
Express multiple “pattern recognition receptors” involved in recognizing broad classes of pathogens
Major growth factor for mast cells
Stem-Cell Factor (SCF), acting on its receptor c-Kit
against they have receptor for IgE
they release histamines
they are tissue based
Basophils
Many similar characteristics than mast cells
Express also IgE receptors
As opposed to mast cells that are more tissue based
Basophils are more circulating in the peripheral blood
Involved in allergic diseases
Play a significant role in the anti-parasitic response
Eosinophils
Eosinophils fight off infectious agents / damage tissues through release of toxic granule proteins such as
- Major Basic Protein
- Eosinophil-Derived Neurotoxin
- Eosinophil Cationic Protein
important against PARASITES
Fighting viral infections through their RNAses contained within their granules.
Ejects DNA of mitochondrial origin producing a sticky network that can capture bacteria and promote their extra-cellular killing
Invaginations of the skin
refer to sweat glands, hair follicles, salivary glands, toot
What are the two forms of epithelial tissue?
Sheet of cell and glands
tissue between a space (fluid/lumen) and the Basement membrane/ basal lamina
What are the derivations of Epithelia
ectoderm - lining of oral and nasal cavities, cornea, skin epidermis & glands of skin
endoderm - lining of GI tract, lining of respiratory tract, liver, pancreas
mesoderm - renal tubules, lining of reproductive tract, lining of blood vessels
What are the functions of epithelia
Function
- protection, thermoregulation
- transport
- secretion
- absorption
- sensations
What are the different nomenclatures for the epithelial layers
Simple Squamous Simple Cuboidal Simple Columnar Stratified squamous (non-keratinized) Stratified squamous (keratinized) Pseudostratified
What percentage of us is made up of skin?
16%
What are the layers of the skin from superficial to deep?
- stratum corneum (cornified or keratinized layer)
- stratum lucidum (clear layer)
- stratum granulosum (granular layer)
- stratum spinosum (spiny layer)
- stratum basale or germinativum (basal layer)
About the Epithelium of Skin
- integument (skin and its appendages)
- skin = epithelium (epidermis) plus dermis (CT) - 16% of body wt
- sits on fatty hypodermis
- dry skin continuous with wet mucous membrane
- skin appendages from epithelium
nails, hair, glands (sweat and sebaceous glands)
What are the layers/parts of the Epidermis-Dermis INTERFACE?
Top/superficial to deeper:
- Tonofilament insertion
- Hemidemosome
- Integrins
- Basement membrane (collagen IV)
- papillary layer
Structures between Stratum Spinosum cells?
These cells are Keratinocytes
- tonofilament bundles converge into the “desmosome” a general term for the structures involved in the attachment
Desmosome includes:
Cadherines: between the cells, attaching them
Tonofilaments and Kerating Filaments
Stratum Spinosum
polyhedral, spiny cells - deeper cells can also be mitotic
- secrete distinct lamellated granules (membrane-coating granules)(mostly glycolipids, not phospholipids)
- intermediate filaments are called tonofilaments
14 keratin (K1 - K14) genes (cytokeratins) in epidermis
70 diseases have been identified with mutated keratin genes
- keratins in spiny processes, insert into desmosomes
Stratum granulosum summary
Stratum granulosum summary
- 3-5 layers of cells
- large keratohyalin granules (no mb, filaggrin protein) assoc. w. tonofibrils (not always present in kerat. epith.)
- lamellated bodies/granules increase in number
- ↑ transglutaminase crosslinking
Stratum Lucidum Summary
Stratum lucidum summary
- thin and variable (in thick skin only), and unstained
- no organelles left, including nucleus
- full of keratin tonofibrils
- cells are dead
Stratum Corneum Summary
Stratum corneum summary
- dead cells, full of crosslinked keratin fibrils, amorphous substance
- protein deposits under membrane as cell envelope (involucrin and loricrin)
- intercellular space packed with lipids
- release of desmosomal attachments
- desquamation, sloughing of squames (cornified cells)
the more mature they are, the more stuffed with keratin they get
Epidermolysis Bullosa
Defective epidermal cell adhesion
Ichthyosis
Abnormal Keratinization of glycolipid processing/release
e. g. filaggrins and transglutaminase mutations
- I think the desquamousing process is messed up so there’s patches of skin, darker or more read that remains
What are other cells, non keratinocytes in the epidermis
Melanocytes
Langerhans cells
Merkel cells
Melanocytes
- function
- derived from?
- location?
- connections to keratinocytes?
- pre-melanosomes contain?
- how is melanin made
mature to melanin granules
- melanin, protects DNA
- cells derive from neural crest
- cell body in stratum basale
- hundreds to thousands per mm2
- no desmosomal connections to keratinocytes
- pre-melanosomes contain tyrosine (amino acid)
- melanosome, tyrosine plus tyrosinase (activated by UV, tyrosine → melanin)
- eu (dark brown) or pheo (red, yellow) melanin
- melanin granules in dendritic-like cell processes
- cytocrine release to keratinocytes
What causes Albinism
- albinism, gene mutations in tyrosinase gene (complete or partial), ↑ skin cancer
tryrosinase is what gets activated by UV light to produce protective melanin
Langerhans cell
- also called dendritic cells (long cell processes)
- bind foreign substances - antigens
- migrating immune response cells that are antigen-presenting cells
- migrate to lymph nodes and present to T lymphocytes
- derive from bone marrow, migratory cells, no desmosomal connections
- 800 cells mm2
- Birbeck (vermiform) granules (function unknown)
Merkel cells
- mechanosensing cells, single isolated cells in basal layer, with desmosomal connections to keratinocytes
- unmyelinated sensory nerve endings contact Merkel cells (complex may act as mechanoreceptor, abundant in finger tips).
- dense-cored granules (function unknown)
Functions of Extracellular Matrix (ECM)
Connecting and supporting (typically collagen fibrils)
collagen = 90% by weight of ECM
- Signals for cell proliferation and differentiation
- Cell communication (outside-in / matrix-cell signaling)
- Cell protection
- Transmits, and attenuates, mechanical signals
- Compartment for blood vessels, lymphatics, nerves, etc.
- Transport system (Ca and other ions, nutrients, metabolites)
- Controls diffusion of soluble growth factors
Connective Tissue
Constituents:
Types:
Constituents: Cells and Extracellular (Intercellular) Matrix
Types: CT proper and CT specialized
CT Proper vs CT specialized
CT Proper
Loose CT (very cellular)
Loose CT (cellular)
[Intermediate CT]
Irregular Dense CT (relatively acellular)
Regular / Oriented Dense CT (relatively acellular)
Nutritive and excretory role
“The battlefield for defence reactions”
Lymph, edema, cancer and metastasis
with addition of mineral = CT Specialized:
Bone, Cartilage and Teeth (dentin, cementum)
What are the major cell types of connective tissue
Mesenchymal cell
Fibroblast (also called Fibrocyte)
Adipocyte
Macrophage / Histiocyte
Mast cell
Plasma cell
Which is the most abundant protein in your body?
Collagen
Collagen is synthesized and secreted by?
Fibroblasts
takes an hour
golgi apparatus is organelle of production?
Dense CT is made up of mostly?
Collagen
Scurvy:
Vit C def
Vit C required for hydroxylation
If absent, no stable triple helices of alpha chains - no ordered fibrils- no collagen- can lead to teeth falling out
Ehlers-Danlos Syndrome
Collagen I, III and V mutations
Gives hyperextensive skin, hyper joint mobility and dislocation
Types of Fibers in our skin
Collagen - fibrillar collagens (types I, II, III, V, VII, XI) Reticular fibres (collagen type III) Elastic fibres (lots of recoil)
Protein cross-linking by which enzyme?
Lysyl Oxidase
Amorphous Ground Substance
(between fibres; resists compressive forces)
Small proteoglycans, e.g. decorin, biglycan
Large proteoglycan aggregates
(glycosaminoglycans, hyaluronic acid and link protein)
Glycoproteins (and other post-translational modifications)
Water, metabolites, mineral ions, etc.
Plasma proteins
Elastin Related Disorders
1. Marfan’s syndrome Fibrillin-1 gene mutations Aortic aneurysm / rupture Lax joints - dislocations Len’s dislocation (ectopia lentis)
- Cutis laxa
Elastin and fibulin-5 mutations, and other elastic fibre degeneration events
Secretory Granules in Skin
Secretory granules, After initial sensitization by antigens, degranulation after IgE binding to Fc receptors
Histamine: vasodilation, edema, hayfever, immediate hypersensitivity Rx, anaphylaxis / effects on SMCs, asthma and bronchiospasms
Heparin: anti-coagulant
Leukocyte chemotactic factors
How deep should a tattoo needle plunge?
only up into the DERMIS
How does hair impact wound healing?
Seems like it gets in the way a bit and delays healing, makes the site less clean
Macrophages can fuse and become foreign-body giant cells around hair/particles in a wound
Granuloma
Nodular encapsulation of macrophages and other cells, followed often by CT (collagen) encapsulation
seen in inactive infections: i.e. TB, or silicon leakage from break implant
What are stretch marks?
In massive enlargement like prganancy, obesity, weight lifters can break collagen fibres/elastic fibers and you’re looking through broken collagen into rich vascular network.
Seeing the blood = early stages, our body starts healing, stem cells to fill in the ruptured collagen and elastin = a scar
What are the three phases of wound healing?
- Hemostasis
- Inflammation
- Proliferation /Maturation
- Remodeling
What type of cells peak INSIDE WOUNDED CELLS during Inflammation vs proliferation phases of wound healing
Inflammation: Neutrophils, than Macrophages, then Fibroblasts start to peak
Proliferation: Fibroblasts continue to peak, then Lymphocytes
Maturation: they all go down* back to normal slowly
What type of cells peak in the MATRIX during Inflammation vs Proliferation vs Maturation phases of wound healing
Inflammation: Fibronectin, the most, then Collagen III
Proliferation: steady increase in collagen I parallel to steady increase in Wound Breaking Strength
Hemostasis of wound healing involves:
Vascular constriction
Clot formation via platelet aggregation/degranulation and fibrin formation
Fibrin clot formation (fibrinogen cleaved by thrombin)
Platelets and surrounding cells release pro-inflammatory cytokines and growth factors
Key growth factors: TGF-β, PDGF, EGF and FGF
Scab (fibrin eschar) or damp clot
Oxygen tension changes
Inflammation phase of wound healing involves:
Neutrophil infiltration, followed by
Monocyte infiltration and differentiation to macrophages.
Lymphocyte infiltration.
Neutrophils clear microbes and cellular debris by phagocytosis, and produce proteases and reactive oxygen species (oxidizes/damages microbial DNA, lipids and proteins).
Macrophages have many roles. Early, release cytokines that recruit and activate more leucocytes, then phagocytosis (everything, including cellular debris and even neutrophil debris [efferocytosis – latin, “burying of the dead cells”]), then secrete factors that stimulate keratinocytes, fibroblasts and angiogenesis.
Cell Proliferation/ Maturation phase of wound healing involves:
Re-epithelialization by keratinocytes.
Angiogenesis.
Fibroblast proliferation and extracellular matrix production (collagen) in the dermis.
Details:
Keratinocyte proliferation and migration
(re-epithelialization) from stratum basale
and hair follicle.
TGF-β1, EGF, KGF, TGF-α, VEGF
Contraction by myofibroblasts (actin-mediated)
In dermis, fibroblast and endothelial cell proliferation
and extracellular matrix production (TGF-β1 effects particularly) (collagen secretion and angiogenesis [need good vascular bed, e.g. so open sores in diabetes], granulation tissue) .
Mesenchymal stem cells (MSCs) for fibroblasts, and hematopoetic stem cells (HSCs) for endothelial cells, arrive from bone marrow via extravasation.
Remodeling phase of wound healing involves:
Regression of capillaries, then normal vascular bed.
Extracellular matrix remodeling via MMPs (matrix metalloproteinases)
Contraction by myofibroblasts (actin-mediated) continues (gradually present in earlier stages)
In cell proliferation stage, which cells produce/responsible for: which cells do: re-epithelialization contraction fibroblasts endothelial cells
Keratinocyte proliferation and migration
(re-epithelialization) from stratum basale
and hair follicle.
TGF-β1, EGF, KGF, TGF-α, VEGF
Contraction by myofibroblasts (actin-mediated)
In dermis, fibroblast and endothelial cell proliferation
and extracellular matrix production (TGF-β1 effects particularly) (collagen secretion and angiogenesis [need good vascular bed, e.g. so open sores in diabetes], granulation tissue) .
Mesenchymal stem cells (MSCs) for fibroblasts, and hematopoetic stem cells (HSCs) for endothelial cells, arrive from bone marrow via extravasation.
What are Dermal Fibroses
They are Hypertrophic scars and Keloids
Overabundance of collagen* in the dermis
Prolonged inflammatory response that leads to increased and sustained ECM* production
Fibroblasts* have increased growth factor receptors and respond more readily to TGF-β*
*key words: collagen, fibroblasts, ECM, TGF-B
Scleroderma
autoimmune disease, localized and systemic
thickening and swelling of the skin
increased collagen- too much*
increased TGF-β and receptors
What are the shared common features of inborn errors of immunity?
Susceptibility to Infection Auto-immunity Auto-inflammation Lymphoprol Neoplasia
Immunodeficiency diseases
- There are two types…
Primary immunodeficiency (PI) diseases are a group of primarily single-gene disorders - early diagnosis/treatment can prevent fatal outcomes**
Secondary (acquired) immunodeficiencies caused by non genetic or external agents
What are Inborn Errors of Immunity
- The three types?
Disorders that may compromise an arm of the immune system
B lymphocytes (Humoral) T lymphocytes (Cellular immunity) Combined (Both T+B cells) Phagocytic arm Complement system
3 types:
Immunodeficiency diseases
Immune Dys-regulation Syndromes
Auto-inflammatory Syndromes
What are some examples of Secondary Immunodeficiencies
This is referring to Acquired immunodeficiency
HIV / AIDS Neoplasia Transplantation (solid organ, stem cells) Functional asplenia / splenectomy Immunosuppressor Anti-metabolic / chemo Radiotherapy Severe malnutrition Uremia, Diabetes ...
What age do genetic disease start at?
ANY AGE
SCID
Severe Combined Immunodeficiency
Diagnosis of IEIs is often….?
IEI= inborn errors of immunity
diagnosis is ofter DELAYED by 4-5 years
half of pts present with permanent functional impairments before diagnosis
Who should be investigated
- there are 10 signs
- Eight or more new ear infections within 1 year
- Two or more serious sinus infections within 1 year
- Two or more pneumonias within 1 year
- Two or more deep-seated infections
- Two or more months on antibiotics with little effect
- Need for intravenous antibiotics to clear infections
- Persistent thrush (white plaques) in mouth or elsewhere on skin, after age 1
- Recurrent, deep skin or organ abscesses
- Failure of an infant to gain weight or grow normally
- A family history of Primary Immunodeficiency
Who should be investigated?
- there are 5 key presentations that should be regarded with high index of suspicion
Infections with
- VERY MILD inflammatory signs
i. e. staph liver abscess with few symptoms: shows deficiency in immune response, red flag - Recurrent autoimmune phenomena
- DYSMORPHIC FEATURES associated with recurrent infection *
- Presence of vaccine pathogen even AFTER vaccination (memory is not working)
- CHRONIC DIARRHEA
What are the top three types in the relative distribution of IEI
- Predominantly antibody deficiencies (humoral)
- Combined immunodeficiencies with associated or syndromic features (humoral and cell mediated arms)
- Congenital defects of phagocyte* number of function
When to suspect a B cell defect
- at what age do they usually present?
Multiple / Severe Bacterial Infections
Respiratory Tract bacterial Infections
Streptococcus, Haemophilis, …
Usually seen after 6 months when maternal antibodies lost
When to suspect a T cell defect
- these are big ones
Opportunistic infections
Candida sp, Pneumocystis jiroveci
Fungal, viral, intra-cellular infections
Diarrhea/Malabsorption
Poor Growth/Failure to Thrive
When to suspect Phagocytic defect?
Characteristically have
Infections of the skin, Liver, GI Tract
Abcesses
Delayed separation of the umbilical cord and wound healing
LAD –>No Pus
Gingivitis/Periodontitis
When to suspect Complement Defect
C1-C4 deficiency
Associated with Rheumatic Disorders
Pyogenic Infections
C5-C9 Complement deficiency Susceptibility to Encapsulated organisms Pneumococcus Meningococcus H. flu
Rheumatism
any disease marked by inflammation and pain in the joints, muscles, or fibrous tissue, especially rheumatoid arthritis.
What should be ordered when suspecting B, T, phagocytic, complement deficiences?
Tests that give you their NUMBER and their FUNCTION
How to determined lymphocyte numbers
CBC : Absolute Lymphocyte Count (ALC)
Flow Cytometry (Fluorescence activated cell sorter: FACS)
Based on the expression of specific molecules at the cell surface called:
CD: Cluster of differentiation
Cell numbers
Cell %age
CD19; for B cells
CD4/CD8/CD3: for T cells
How to determine B cell FUNCTION?
Quantitative
IgG
IgM
IgA
IgE
Qualitative
Serology
I think for serology you’re looking for the presence of bacterial elements that you should have memory ab for there fore they should not be circulating in your blood?
Tetanus Diphtheria H. flu MMR Hepatitis Pneumococcus …
AND DNA sequencing
How to test for T cell function ?
4 main types
CD4: Helper
- B cells Antibody levels
Assessing their proliferation abilities in response to
a. Mitogens
Causing widespread lymphocyte activation (proliferation)
- Isolated from plants and bacteria
The most used are:
Phytohemagglutinin (PHA): stimulate T lymphocytes Concanavalin A (Con A): stimulate T lymphocytes Pokeweed mitogen (PWM): stimulate both T and B lymphocytes
Specific antigens (Tetanus, CMV…)
ALSO T4 hypersensitivity test: Anergy skin test, PPD for TB
and DNA sequencing
How to detect defects in phagocytic arm? (number)
Nb.
CBC: ANC…
- Neutropenia
- Neutrophelia
Leukocyte Adhesion Deficiency (LAD):
Lack of adhesion molecules: CD18
How to detect defects in the FUNCTION of phagocytic arm?
Function
Chronic Granulomatous Disease (CGD): DHR
Phagocytic cells reduce DHR to the strongly fluorescent compound Rhodamine
Flow cytometry
Individual fluorescent cells counted
Amount of fluorescence per cell is quantified
and ofc DNA sequencing
What are the three compliment pathways
- Classical pathway: ab binding to invaders
- Lectin pathway: mannose binding lectin binding to invaders
- Alternative pathway: C3b binding to microbial invaders
these all lead to opsonization, inflammatory upregulation, and MAC lysis of cells
How to quantify Nb for complement system?
Dosage of each individual component of the system
eg. C3, C4,…
How to measure complement system FUNCTION?
ELISA
An enzyme immunoassay
Stimulation with specific activators of the
Classical pathway
Alternative
MBL
Amount of MAC (C5b-9) generated measured
- For each pathway
Examples of monogenic/primary IEI
XLA: X Linked Agammaglobulinemia
CD18: Leukocyte Adhesion Deficiency
Some clinical features of autoimmunity
arthritis, thyroid, cytopenias
Infectious Agents Associated with B cell Immune Defects
Encapsulated bacteria: Pneumococcus Haemophilus Meningococcus Pseudomonas Sinusitis, otitis, pneumonia Bacteremia, meningitis, arthritis, osteomyelitis Enteroviruses (RNA viruses, start in GI, spread to CNS) Giardia (gut)
Infectious Agents Associated with T cell immune defects
T cell:
Viruses HSV, CMV, VZV, EBV Severe protracted LRTI (RSV, paraflu, flu, adeno) Fungi Mucocutaneous or disseminated candidiasis PCP Mycobacteria Protozoa Toxoplasma Intestinal protozoans Strongyloides
What are some Red Flags for Primary Immunodeficiency
Repeated invasive infection
Infections with opportunistic pathogens
Poor response to prolonged antibiotic therapies
chronic diarrhea
Chronic failure to gain weight and grwo
Persistent/ Recurrent oral lesions, skin rashes
Family history
What is XLA
X-Linked Agammaglobulinemia
Arrest of B cell development at pre-B cell stage (meaning still in the bone marrow… none will make it to circulation)
Mutation in btk gene (Bruton tyrosine kinase)
Autosomal recessive* for other enzymes involved in the pathway: i.e. BLNK
What are the presentations and findings in people with XLA?
- age of infections
- serology/CBC findings
- susceptible to…?
Infections begin at 4-6 months when maternal immunity wanes
Absent circulating mature B cells
All major classes of immunoglobulin affected (IgG, IgM, IgA)
No antibody responses to antigen
Sino-oto-pulmonary infections with encapsulated bacteria
Bacteremia, meningitis, septic arthritis, etc
Chronic infections with enteroviruses
IgG levels in infants
Immunoglobulin levels in the fetus and in the infant. As maternal IgG declines, total IgG reaches a lowest point between 3 and 6 months of age, after which it rises as the endogenous IgG increases with age. Premature infants are born with lower IgG and have a deeper and longer lowest points. THI is a delay in recovery from the nadir.
IgG level goes up in the last trimester before birth
After birth it goes down once umbilical cord is cut
Liquid Protection
- some examples
- what is it used for?
IVIG: Intravenous immune globulin
SQIG: Subcutaneous Immunoglobulin (SCIg)
Perscribed for Ab deficiencies
SCID
- cause
- clues in CBC
- presentation
SCID = Severe Combined Immunodeficiency
Cause:
Severe defect in T cell development
No T cells, +/- B cells or NK cells
CBC findings:
Lymphopenia is an early clue
Also severe antibody deficiency
Presentation:
Extreme susceptibility to infection since birth to high-grade or low-grade pathogens
Protracted diarrhea, failure to thrive
Death from infection before 1 year unless transplanted
What are some enzymes that are impaired that can leads to SCID/T cell defects
JAK-3 IL7Ra RAG 1/2 ADA MHC II MHC 1, ZAP 70
memorize this order for the phenotypes chart
JAK has 7 RAGs
Lymphocyte phenotypes in SCID for JAK defect
How it impacts: CD4, CD8, B, NK cells
only B cells are present
no T cell of NK cell development
Lymphocyte phenotypes in SCID for IL7Ra defect
How it impacts: CD4, CD8, B, NK cells
both B and NK cells are present
NO T cells
Lymphocyte phenotypes in SCID for RAG1/2 defect
How it impacts: CD4, CD8, B, NK cells
Only NK cells are present
no T or B cells
Lymphocyte phenotypes in SCID for ADA defect
How it impacts: CD4, CD8, B, NK cells
NONE are present
Lymphocyte phenotypes in SCID for MHC 1 defect
How it impacts: CD4, CD8, B, NK cells
only CD8 is absent,
all the others, CD4, B. NK are present
Lymphocyte phenotypes in SCID for MHC II defect
How it impacts: CD4, CD8, B, NK cells
only CD4 is absent
all the other, NK, B, CD8 are present
Ommen Syndrome
Hypomorphic Rag1/Rag2 mutation: Leaky phenotype (null mutation=SCID)
Limited amount of T cell clones produce in thymus: oligoclonal expansion/activation of T cells that are autorreactive (anti-self)=T+B-NK+
ATTENTION: No Lymphopenia!
Cause desquamating erythroderma, fever, hepatosplenomegaly, lymphadenopathy, eosinophilia, high IgE, diarrhea, FTT
Profound immunodeficiency, need HSCT
May occur with other SCID, DiGeorge
What are some examples of Primary T cell Deficiences
SCID
DiGeorge Syndrome
Wiskott-Aldrich syndrome
Ataxia- Telangiectasia
What mutations puts Boys in trouble for PID?
X-linked ones:
No BTK = no B cells/abs, XLA
No y common chain = no T cells (XL-SCID)
What is Central Tolerance?
When an immature lymphocyte recognises/reacts to a self antigen in a primary lymphoid organ (thymus/ bone marrow), it receives a negative signal causing its death or inactivation
- purpose is to ELIMINATE strongly autoreactive lymphocytes
this is a form of POSITIVE selection? you keep the ones that DON’T react?
What is Peripheral Tolerance?
Encounter of a naïve lymphocyte with antigen in the absence of co-stimulation leads to
a. anergy: survives but is mute, doesn’t get activated
b. deletion: apoptosis or
c. induction of a T regulatory* response
Now these are with MATURE lymphocytes
Elimination of Mature lymphocytes that recognize/react to self antigens
how it works:
Strong, constant signal of self antigens that constantly surround them through naïve lymphocyte receptors induces tolerance
Sudden increase in foreign antigen-receptor signal in naïve lymphocytes activates them
What are the 4 functions of T reg cells?
- stimulated by which cytokines
a. Inhibitory cytokines
TGFb, IL10, IL35 inhibit Effector T cells
b. cytolysis: granzymes and perforin pores: apoptotic effects
c. Metabolic disruption
d. Targeting dendritic cells
this is a type of PERIPHERAL tolerance
Role of AIRE in defective central tolerance
Normal condition: Under the control of the AIRE protein, thymic medullary cells express tissue-specific proteins, deleting tissue-reactive T cells
in DEFECTIVE central tolerance
the ABSENCE of AIRE T cells reactive to tissue specfic antigens MATURE and leave the thymus. oop
APECED
AIRE mutation
- defective central tolerance in Thymus
- presents in childhood
polyendocrinopathy
Candidiasis
Ectodermal dysplasia
What are the types of defective PERIPHERAL tolerances?
a. Molecular mimicry: self cells resemble foreign antigens that our body is making ab for
b. Epitope spreading: during cell death, release of intracellular antigens for which we are NOT tolerant too can trigger ab production
c. Bystander Activation: activation of anergic (defective cells) incases of severe infection/high immune activation
d. cryptic antigens: invade BBB which should otherwise be segregated, and created ab to self.
What are the THREE mechanisms of defective tolerance?
a. defective central tolerance
b. defective peripheral tolerance
c. defective T regulatory response
IPEX
Immunodysregulation
Polyendocrinopathy (hypothyroidism)
Enteropathy
X- linked
this is a defective T regulatory* response
involves mutation in FOXP3
associated with T1 diabeted, enteropathy (98%) eczema, and hypotheyroidism
Role of Genetics in Autoimmune conditions
Strong evidence for genetic involvement HOWEVER
** INTERPLAY between genetic background and environment: patients with similar backgrounds will develop disease at different moment of their lives **
Which genotypes has the STRONGEST association with Auto-Immunity?
MHC*
they are better at presenting self antigens that others.
What happens if you have a mutant NOD2
This is an examples of how genetic defects that impair INNATE immunity can lead to AUTOIMMUNITY
lack of NOD2 function = loss of ability to sense peptidoglucan = loss of protective inflammatory barrier = infiltration of bacteria = chronic inflammation
Causes of Chronic/systemic autoimmunity
Chronic autoimmunity develops via
a. persistence of self antigens,
b. uncontrolled inflammation and
c. epitope spreading
What are examples of organ specific autoimmune disease
Type 1 diabetes good pastures syndrome MS Gravies Myasthenia gravis (type 2)
What are some examples of systemic autoimmune diseases?
RA (type 3) scleroderma SLE (type 3)
Myasthenia GRavis
type 2: ADCC, blocking and activation pathways
ab bind to ach receptors, which inhibits neuronal signalling
Proptosis/diplopia
Oropharyngeal muscle weakness
Trouble chewing/swallowing/talking
Worse with repetitive movement
Worse end of the day
Myasthenia crisis: respiratory muscle insufficiency
Major affected organ for Type 3 hypersensitivity?
KIDNEYS: glomerulonephritis
also affects skin (vasculitis) and joints (RA)
What type of hypersensitvity is Diabetes
TYPE 4
T cell, cytotoxicity against insulin cells in pancreas (destruction of insulin)
What is Asthma
Reversible, obstructive airway disease
- 12-15% change in pulmonary function (FEV1= Forced Expiratory Volume in one Second) after an inhaled bronchodilator (eg. salbutamol)
- Decrease in FEV1 by 20% of baseline following the inhalation of methacholine or histamine (up to a maximum of 16mg/ml)
- Decrease in FEV1 by 15-20% following standardized exercise challenge
Spectrum of Asthma
Mild, episodic
Mild chronic
Moderate
Severe
What is the relationship between Allergy and Asthma
- 70% of childhood asthmatics have allergies
- 50% of adult asthmatics have allergies
- Many asthmatics have increased “bronchial reactivity” because of pets or dust mites
- Only a small number of asthmatics complain that they wheeze from their own pets, but that does not mean their lungs aren’t affected.
What are symptoms of asthma
Daily symptoms Nocturnal symptoms Exercise induced symptoms Symptoms with normal daily activities Viral respiratory tract infection induced symptoms Allergy-induced symptoms
symptoms:
Cough
Shortness of breath
Chest tightness
Signs: Coughing Rapid breathing Accessory muscle use Hypoxia Poor air entry Wheeze
Which cytokines are released by Th1
Intracellular organisms
IFN-γ, IL-12, IL-18
pretty sure this one is macrophage specific
Which cytokines are released by Th2
Antibody production, parasite defense, allergy
IL-4, IL-5, IL-13
Th17
Antibacterial, antifungal
IL-17, IL-22
Treg
Immune Response Regulation
IL-10, TGF-B
What are some treatments for asthma?
Anti-inflammatory (steroids, glucocorticoids)
Anti mediators (anti histamines)
Anti-IgE: Omalizumab
Omalizumab
anti-IgE antibodies
used to treat asthma
- affects both early and late phase asthma response
What is the ab structure?
arms: antigen binding site, light chains (lambda, kappa)
legs: heavy chain, Fc receptor
How do you make monoclonal antibodies
- a mouse injected with antigen
- produces B cells-> antibodies
- plasma cells are collected, and mixed with tumor cells
- hybrid cells grow, to produce ab at high rate
- pure tumor cells are harvested
IL4 and IL13 signal through which two receptors
Type 1: B cells, T cells, monocytes, eosinophils, fibroblasts
Type 2: epithelial cells, smooth cells, fibroblasts, monocytes, activated b cells.
Dupilumab
Is a Human Monoclonal Antibody That Binds Specifically to IL-4Rα and Inhibits Signaling by Both IL-4 and IL-13
these cytokines are involved in Th2 -> IgE -> mast cells, eosinophil degranulation
effective in clinical trial
What are the targets of IgE therapy?
Omalizumab:
2 pathways
a. Binds to circulatin IgE, decreasing cell bound IgE
- decreases tissue infiltration
b. Decreases expression of high affinity receptors
- decreases mediator release
BOTH ultimately decrease asthma symptoms and exacerbations
