Kaplan - Immunology Flashcards
What is the body’s first line of defense and what are its defensive barriers?
Innate Immunity
- Anatomic/Physical (skin, mucous membranes, flora)
- Physiologic (temperature, pH, antimicrobials, cytokines)
- Complement
- Cellular: Phagocytes and granulocytes
- Inflammation
Which immunity has no memory, limited specificity, present intrinsically?
Innate immunity
What makes up the adaptive immunity?
T lymphocytes
B lymphocytes
Their effector cells
What is immunologic memory?
Are capable of distinguishing self from non self
What is the difference between Sensitivity and Specificity?
Sensitivity (also called the true positive rate) measures the proportion of positives that are correctly identified as such (e.g. the percentage of sick people who are correctly identified as having the condition).
Specificity (also called the true negative rate) measures the proportion of negatives that are correctly identified as such (e.g. the percentage of healthy people who are correctly identified as not having the condition).
What is Sensitivity?
Sensitivity (also called the true positive rate) measures the proportion of positives that are correctly identified as such (e.g. the percentage of sick people who are correctly identified as having the condition).
What is Specificity?
Specificity (also called the true negative rate) measures the proportion of negatives that are correctly identified as such (e.g. the percentage of healthy people who are correctly identified as not having the condition).
What is self-limitation and why do we need it?
allows the system to return to a basal resting state after a challenge to conserve energy and resources and to avoid uncontrolled cell proliferation resulting in leukemia or lymphoma.
Which type of immunity has the ability of self-reactivity?
Neither, idiot
What are the anatomic and physiologic barriers of the two types of immunity?
Innate: skin, mucosa, normal flora, temperature, pH, antimicrobials, and cytokines
Adaptive: lymph nodes, spleen, mucosal-associated lymphoid tissues
What are the cell types of the two types of immunity?
Innate: Phagocytes, granulocytes, and natural killer
Adaptive: B lymphocytes and T lymphocytes
What are the blood proteins of the two types of immunity?
Innate: compliment
Adaptive: Antibodies
How long does it take the adaptive immune response to begin clearance of the infection through the action of effector cells and antibodies?
AKA when does the adaptive immune response begin?
1 - 2 weeks after primary infection for the adaptive immune response to begin clearance of the infection
What kind of mechanism does the innate and adaptive immune system use to work together?
Positive feedback mechanism
What is ontogeny/ontogenesis?
the development of an individual organism or anatomical or behavioral feature from the earliest stage to maturity.
What is hematopoiesis?
Production, development, differentiation and maturation of the blood cells (erythrocytes, megakaryocytes, and leukocytes) from multipotent stem cells.
Which cells are considered blood cells?
Erythrocytes
megakaryocytes
leukocytes
From which cell is hematopoeisis derived from?
multipotent stem cells
site of hematopoiesis during embryogenesis and early fetal development?
yolk sac
site of hematopoiesis during organogenesis?
liver and spleen
site of hematopoiesis during adulthood?
bone marrow
What kind of division do multipotent stem cells go through in the bone marrow?
asymmetric division
What do the two daughter cells from asymmetric division from multipotent stem cells from bone marrow do?
- self renewal
2. gives rise to either a common lymphoid progenitor cell or a common myeloid progenitor cell (potency)
Common Lymphoid progenitor cells give rise to:
B lymphocytes, T lymphocytes, and Natural Killer cells
Common Myeloid progenitor cells give rise to:
erythrocytes, megakaryocytes/thrombocytes, mast cells, eosinophils, basophils, neutrophils, monocytes/macrophages, and dendritic cells
Are natural killers innate or adaptive immunity?
NK are from lymphoid lineage but participate in innate immunity.
What differences of cell lineage does the B and T lymphocytes have?
B lymphocytes remain within the BONE MARROW to complete their development.
T lymphocytes leave the bone marrow and undergo development within the THYMUS.
What is the Third lymphocyte?
Natural Killers; they recognize tumor and virally infected cells through non specific binding.
What is the most abundant circulating blood cell?
Neutrophril or polymorphonuclear (PMN) cell
Neutrophril or polymorphonuclear (PMN) cell function?
Phagocytic activity aimed at killing extracellular pathogens.
lymphocyte cell function?
No function until activated in secondary
plasma cell function?
Terminally differentiated B lymphocyte that secretes antibodies.
Natural Killer Cell function?
Kills virally infected cells and tumor cells.
Monocyte function?
Precursor of tissue macrophage
Macrophage function?
Phagocyte
Professional Antigen presenting cell
T-cell activator
Dendritic cell function?
Phagocyte
Professional Antigen presenting cell
T-cell activator
Eosinophil function?
Elimination of large extracellular parasites
Type 1 hyperxdennsitivity
Mast cell function?
Elimination of large extracellular parasites
Type 1 hypersensitivity
Basophil function?
Elimination of large extracellular parasites
Type 1 hypersensitivity
Physical description:
Granulocyte with a segmented lobular nuclei (3-5 lobes) and small pink cytoplasmic granules
Neutrophil or Polymorphonuclear (PMN) cell
Physical description:
Large, dark staining nucleus with a thin rim of cytoplasm.
Lymphocyte
Surface markers:
B lymphocytes:
CD19, 20, 21
Surface markers:
T lymphocytes:
CD3
Surface markers:
Helper T cells:
CD4
Surface markers:
CTLS:
CD8
Physical description:
Small eccentric nucleus, intensely staining Golgi Aparatus.
Plasma Cell
Physical description:
Lymphocyte with large cytoplasmic granules
Natural Killer Cell
Surface markers:
Natural Killer Cells
CD 16, 56
Physical description:
Agranulocyte with a bean or kidney shaped nucleus.
Monocyte
Physical description:
Agranulocyte with a ruffled cytoplasmic membrane and cytoplasmic vacuoles and vesicles.
Macrophage
Physical description:
Agranulocyte with thin, stellate cytoplasmic projections
Dendritic cell
Physical description:
Granulocyte with bilobed nucleus and large pink cytoplasmic granules
eosinophil
Physical description:
Granulocyte with small nucleus and large blue cytoplasmic granule
Mast Cell
Physical description:
Granulocyte with bilobed nucleus and large blue cytoplasmic granules
Basophil
What is the most common leukocyte evaluated in a WBC differential of an adult?
Nuetophils (PMNs) 50-70%
What are the 2 isotopes of antibody or immunoglobulin expressed on surface membrane of mature, naive B lymphocytes?
IgM
IgD
What is expressed on surface membrane of mature, naive T lymphocytes?
T-Cell receptor (TCR)
Heavy chain and Light chain are the membrane bound immunoglobulin of which type of lymphocyte?
B lymphocyte
What holds together a heavy and light chains?
disulfide bond which makes the two halves resemble a “Y” shape
What is the “Y” shape of the B lymphocyte called?
hinge region
Which antigen receptor has:
- membrane bound immunoglobulin
- is a 4 chain glycoprotein molecule
- two halves held together by disulfide bond
- shape resembling “Y”
- hinge region
- flexible
Antigen receptor of the B lymphocyte
Which antigen receptor has:
- alpha chain
- beta chain
- antigenic peptide complexed to an MHC molecule
- No hinge region –> rigid
Antigen receptor of the T lymphocyte
the membrane receptors of B lymphocytes are designed to bind ______
unprocessed antigens of almost any chemical composition ie. polysaccharide, proteins, lipids,
the membrane receptors of TCR are designed to bind ______
peptides complexed to MHC
What is the signal transduction complex?
When a lymphocyte binds to an antigen complementary to its idiotype, a cascade of messages transferred through its signal transduction complex will culminate in intracytoplasmic phosphorylation events leading to activation of the cell.
CD21 is the receptor to what?
EBV
CD81 is the receptor to what?
Hepatitits C and Plasmodium vivax
How do B lymphocyte progenitors produce heavy chain variable domains?
B lymphocyte progenitors select randomly and in the absence of stimulating antigen to recombine 3 gene segments designated variable (V), diversity (D) and joining (J) out of hundreds of gremlin encoded possibilities to produce unique sequences of amino acids in the variable domains (VDJ recombination)
What is an idiotype?
antigen specificity
What is the point in VDJ rearrangements in DNA?
to produce the diversity of heavy chain variable domains
The enzymes responsible for gene rearrangements in lymphocyte development are called?
RAG1 and RAG2
The B-lymphocyte progenitor performs random rearrangements of 2 types of gene segments to encode the variable domain amino acids of the light chain. which are the two gene segments?
V and J
VJ rearrangements in DNA produce the diversity of light chain variable domains.
What is the function of the enzyme terminal deoxyribonucleotidyl transferase (Tdt)?
While heavy chain gene segments are undergoing recombination the enzyme Tdt randomly inserts bases (without a template on the complementary strand) at the junctions of V, D, J segments (n-nucleotide addition)
What is the function of N-nucleotide addiotn?
The random addition of the nucleotide generates junctional diversity.
What is apoptosis?
Programmed cell death
What is the function of allelic exclusion?
The process that ensures that B and T lymphocytes synthesize only ONE specific antigen receptor per cell.
Which cells are capable of N-nucleotide addition?
B cells (only heavy chain) T cells (all chains)
Omenn Syndrome:
Genetics?
Molecular defect?
Symptoms?
Omenn Syndrome:
Genetics: Autosomal recessive
Molecular defect: Missense mutation in RAG genes. The RAG enzyme have only partial activity.
Symptoms:
- Lack of B cells (below limits of detection).
- Marked decrease in predominantly Th2
- Characterized by early onset, failure to thrive, red rash (generalized), diarrhea, and severe immune deficiency.
Severe Combined Immunodeficiency (SCID):
Genetics?
Molecular defect?
Symptoms?
Genetics: Autosomal recessive
Molecular defect: Null mutations in RAG1 or RAG2 genes. No RAG enzyme activity.
Symptoms:
- Total lack of B and T cells.
- Total defects in humoral and cell mediated immunity.
What kind of lymphoid organ is the bone marrow?
Primary lymphoid organ.
As lymphoid progenitors develop in the bone marrow, they make random rearrangements of their germline DNA to produce the unique idiotypes of antigen-recognition molecules that they will use throughout their lives.
What is clonal deletion and clonal anergy?
clonal deletion: cells deleted in bone marrow
clonal anergy: cells inactivated in the periphery
Which are the only b lymphocytes released to the periphery and allowed to leave the bone marrow?
Selectively unresponsive (tolerant) to self antigens are allowed to leave the bone marrow.
What is the second primary lymphoid organ?
Thymus, the second primary lymphoid organ dedicated to maturation of T cells.
How is a pre thyme cell considered a double negative T lymphocyte?
If they do not express CD4 or CD8 on their surface
What is a double positive thymocyte?
T-cell receptors that coexpress the CD3 complex as well as the CD4 and CD8 co receptors
What is MHC, whats their function?
To avoid binding to normal self-antigens and cause autoimmunity, Major Histocompatibility complex exposed developing thymocytes to high level of unique group of membrane bound molecules.
Where are the MHC located at?
They are membrane bound molecules.
Are a collection of highly polymorphic genes on the short arm of chromosome 6 in the human.
What is another name for MHC gene products?
human leukocyte antigens (HLA)
Name the gene products of Class I MHC:
HLA-A, HLA-B, HLA-C
Name the gene products of Class I MHC:
HLA-DM, HLA-DP, HLA-DQ, HLA-DR
Where are class I molecules expressed on?
All nucleated cells in the body, as well as platelets.
In what kind of fashion are class I molecules expressed?
Codominant fashion, meaning that each cell expresses 2 A, 2 B, 2 C products (one from each parent).
Where are class II molecules expressed on and in what fashion?
Class II MHC molecules are expressed (also codominantly) on the professional antigen-presenting cells of the body (primarily the macrophages, B lymphocytes, and dendritic cells).
In terms of MHC, what are:
positive selection
failure of positive selection
negative selection
● Those that have TCRs capable of binding with low affinity will receive a positive selection signal to divide and establish clones that will eventually mature in the medulla.
● Those that fail to recognize self-MHC at all will not be encouraged to mature (failure of positive selection).
● Those that bind too strongly to self MHC molecules and self-peptide will be induced to undergo apoptosis (negative selection) because these cells would have the potential to cause autoimmune disease.
How do thymocytes decide to become CD4 or CD8?
Although double positive thymocytes co-express CD4 and CD8, the cells are direct- ed to express only CD8 if their TCR binds class I molecules, and only CD4 if their TCR binds class II molecules
Which cells become “helper” cells (Th cells) and which cells become Cytotoxic T lymphocytes (CTL)?
CD4+ cells that recognize class II MHC are destined to become “helper” T cells ( ), and CD8+ cells that recognize class I MHC are destined to become cytotoxic T lymphocytes (CTLs).
What are regulatory T cells (Tregs) and what is their function?
Tregs inhibit self-reactive Th1 cells in the periphery.
● Identified by their constitutive expression of CD25 on the surface and by the expression of the transcription factor FoxP3
● Secrete IL-10 and TGF-β which inhibit inflammation
● Shown to be critical in the prevention of autoimmunity
What is the primary job of a cytokine?
initiate an inflammatory response
What can a defensin found in a phagocyte do?
They can cause pores in bacteria and fungi.
Phagocytic cells are part of the first line of defense against invading pathogens. They recognize pathogens via shared molecules that are not expressed on host cells. They are responsible for controlling the infections and sometimes are even capable of eradicating them.
Name the most common phagocytic cells.
monocytes/macrophages, neutrophils and dendritic cells
What are the receptors of the innate immune System and what is it function?
Pattern recognition receptors (PRRs).
They recognize pathogen associated molecular patterns (PAMPs) or damage associated molecular patterns (DAMPSs)
The inflammasome is an important part of the innate immune system. It is expressed in myeloid cells as a signalling system for detection of pathogens and stressors. Activation of the inflammasome results in the production of _________ and ________, which are potent in inflammatory cytokines.
IL-1β and IL-18
Which myeloid cells are CD14 positive?
Monocyte, macrophage, Neutrophil, dendritic cells
Which innate immunity cells is this:
● Circulating phagocytes
● Short lived
● Rapid response, not prolonged defense
Neutrophils
Which innate immunity cells is this:
● Provide a prolonged defense
● Produce cytokines that initiate and regulate inflammation
● Phagocytose pathogens
● Clear dead tissue and initiate tissue repair
Monocytes/ macrophages
Whats the relationship of a Monocytes/ macrophages?
Monocytes circulate in the blood, become macrophages in the tissues
What are the two pathways for macrophage activation?
Classical M1:
Induced by innate immunity (TLRs, IFN-y)
Phagocytosis, initiate inflammatory response
Alternative M2:
Induced by IL-4, IL-13
Tissue repair and control of inflammation
Which innate immunity cells is this:
● Found in all tissues
● Antigen processing and presentation
● Two major functions: initiate inflammatory response and stimulate adaptive immune response
Dendritic Cells (DCs)
Which innate immunity cells is this:
● Skin, mucosa
● 2 pathways for activation: innate TLRs and antibody-dependent (IgE)
Mast cells
Which innate immunity cells is this:
● Blood, periphery
● Direct lysis of cells, secretion of IFN-γ
Natural Killer Cells (NK cells)
The complement system is a set of interacting proteins released into the blood after production in the liver. The components act together as zymogens, activating one another in cascade fashion after initiation from a variety of stimuli.
What are the 3 functions of the complement system?
- Recruitment of inflammatory cells and anaphylatoxins
- Opsonization of pathogens
- Killing of pathogens
What is Leukocyte adhesion deficiency (LAD) and what are its symptoms?
Rare autosomal recessive disease in which there is an absence of CD18 (the common B2 chain of a number of integral molecules).
A key element in the migration of leukocytes is integrin-mediated cell adhesion; patients suffer from an inability of their leukocytes to undergo adhesion dependent migration into sites of inflammation.
opmphalitis, abscess and pus do not occur, more susceptible to recurrent, chronic bacterial infections.
What is the first indication of Leukocyte adhesion deficiency (LAD)?
The first indication of this defect is often omphalitis, a swelling and reddening around the stalk of the umbilical cord.
How do you diagnose Leukocyte adhesion deficiency (LAD)?
Evaluating expression (or lack) of the B chain (CD18) f the intern by flow cytometry.
What are the five steps of phagocytosis?
- Extension of pseudopodia to engulf attached material
- Fusion of the pseudopodia to trap the material in a phagosome
- Fusion of the phagosome with a lysosome to create a phagolysosome
- Digestion
- Exocytosis of digested contents
What is pus?
Neutrophils release granule contents into extracellular milieu during phagocytosis and inflammation in which the neutrophils die, forming what is known as pus.
What is a respiratory burst and what are the two oxygen dependent mechanisms of intracellular digestion that are activated as a result of this process?
During phagocytosis, a metabolic process known as the respiratory burst activates a membrane-bound oxidase that generates oxygen metabolites, which are toxic to ingested microorganisms. Two oxygen-dependent mechanisms of intracellular digestion are activated as a result of this process.
● NADPH oxidase reduces oxygen to superoxide anion, which generates hydroxyl radicals and hydrogen peroxide, which are microbicidal.
● Myeloperoxidase in the lysosomes acts on hydrogen peroxide and chloride ions to produce hypochlorite (the active ingredient in household bleach), which is microbicidal.
What is hypochlorite?
the active ingredient in household bleach
What is Chronic granulomatous disease (CGD)?
an inherited de ciency in the production of one of several subunits of NADPH oxidase. This defect eliminates the phagocyte’s ability to produce many critical oxygen-dependent intracellular metabolites.
• If the patient is infected with a catalase-positive organism (e.g., Staphylococcus, Klebsiella, Serratia, Aspergillus), the myeloperoxidase system lacks its substrate (because these organisms destroy H2O2), and the patient is left with the oxygen- independent lysosomal mechanisms that prove inadequate to control rampant infections.
Thus, CGD patients suffer from chronic, recurrent infections with catalase-positive organisms.
What are some catalase positive organisms?
Staphylococcus, Klebsiella, Serratia, Aspergillus
How can you detect failures of phagocytic cells to generate oxygen radicals?
Nitroblue tetrazolium (NBT) reduction tests or neutrophil oxidative index (NOI; a flow cytometric assay).
The dihydrorhodamine test -a similar test using flow cytometry may be used.
How can you tell if the results of a nitro blue tetrazolium reduction are normal or abnormal?
Normal: formazan positive (purple-blue)
Abnormal: formazan negative (yellow)
The innate response to viruses is unique in that it is geared toward eliminating these intracellular pathogens. The 2 major mechanisms for dealing with viral infections are ________.
IFN-α/β
NK cells.
How do interferons work on viruses?
Act on target cells to inhibit viral replication, not the virus.
Are not virus-specific
What are the therapeutic uses of IF alpha?
has well-known antiviral activity and has been used in the treatment of hepatitis B and C infections.
Within cancer therapy, it has shown promise in treatment of hairy B-cell leukemia, chronic myelogenous leukemia, and Kaposi sarcoma.
What are the therapeutic uses of IF beta?
was the first drug shown to have a positive effect on young adults with multiple sclerosis. Patients treated with It enjoy longer periods of remission and reduced severity of relapses.
What are the therapeutic uses of IF y?
being used in the treatment of chronic granulomatous disease (CGD). This molecule is a potent inducer of macrophage activation and a promoter of inflammatory responses. Its application appears to significantly reverse the CGD patient’s inability to generate toxic oxygen metabolites inside phagocytic cells.
What increases the activity of NK?
NK activity is increased in the presence of interferons (IFNs) a and b and IL-12
NK cells employ 2 categories of receptor:
NK cells employ 2 categories of receptor: killer activating receptor (KAR) and killer inhibitory receptor (KIR).
If only KARs are engaged, the target cells will be killed. If both the KIRs and the KARs are ligated, the target cell lives. Therefore the inhibitory signals trump the activation signals.
What is NKG2D?
NKG2D is a major KAR expressed by NK cells.