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22 Cards in this Set
- Front
- Back
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How do signaling proteins fire in BCR/TCR activation (signal transuction)? Will the signal always be the same? |
1) antigen receptors associate with cellular signaling proteins in the BCR/TCR complex 2) Binding of 2 or more antigens by adjacent receptors result in the receptors being pulled together into an aggregate 3) cross-linking brings signaling proteins together and initiates signal transduction -->b/c signaling proteins are the same in each clone, the transduced signal is also the same |
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Where do B cells arise from? |
Bone marrow stem cells |
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True or False: Each B cell encodes its own unique BCR but has similar antigen specificity to other B cells |
First part is true but second part is false: B cells encode their own specific BCR with their own unique antigen specificity |
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True or false: The BCR and corresponding antibody share identical antigen specificities |
TRUE --> an antibody is a secreted version of a BCR wtih identical antigen specificity (this means that the antibody targets the exact same antigen that initially stimulated the BCR) |
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What do antibodies consist of? |
4 polypeptides: 2 identical light chains and 2 identical heavy chains for a Y-shaped molecule |
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How are light chains and dark chains connected? |
Disulphide bridges --> give stability and flexibility |
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What does a light chain contain? |
One variable (V) domain and one constant (C) domain |
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What does a heavy chain contain? |
One variable (V) domain and at least 3 constant (C) domains |
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Each domain folds into what? |
a characteristic 3D shape: The Immunoglobulin (Ig) domain |
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Each antigen receptor has 2 distinct functional domains. What are they and what do they do? |
1) Each BCR/antibody has its own unique v region and is involved in antigen recognition 2) All BCRs/antibodies share a common constant region and is required for structural integrity and effector function |
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What is a epitope? |
-the parts of an antigen recognized by an antibody -can be recognized on the basis of sequence and shape |
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What is affinity? |
the strength with which one antigen-binding surface of an antibody binds an antigen |
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What are 3 features of antibody-mediated antigen recognition? |
1) antibodies recognize a large array of 3D structures 2) each clone is specific for a single antigen 3) signaling triggers B lymphocyte action |
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What are the 5 Immunoglobulin isotypes? |
1) IgA 2) IgD 3) IgE 4) IgG 5) IgM |
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What is the role of the IgA isotype? |
-2 IgA molecules are joined by a J chain -the J chain facilitates transport of IgA across mucosal epithelia -J chain also facilitates transfer of IgA to newborns to confer neonatal passive immunity |
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What is the role of the IgD isotype? |
Unknown!! -no major defects in mice lacking IgD |
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What is the role of IgE? |
-secreted as a monomer -binds the Fc-epsilon receptors of mast cells -when IgE is cross-linked by antigen, it triggers mast cell degranulation - allergic response -possible anti-parasitic funtion |
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What is the role of IgG? |
-secreted as a monomer -binds and neutralizes toxins -opsonization: coats pathogens and prevents them from entering host cell |
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What usually happens to opsonized microbes? |
-they are targets for phagocytosis for macrophages (adaptive and innate immune systems working together!) -get degraded in phagolysosome -microbial peptides are presented on MHC II molecules - CD4 T cell activation! |
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What is something else that Fc receptors do? |
mediate antibody-dependent cellular cytotoxicity (ADCC) -Fc-gamma receptors on NK cells bind Fc of Ig -cross-linking of Fc receptors signals to NK cells to kill target cells -target cells killed by apoptosis -another case of adaptive activating innate!!! |
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What is the role of IgM? |
-exists as a pentamers (10 different antigen binding sites!) -has a J chain for secretion (like IgA) -is the first antibody expressed in mature B cells -activates the complement pathway (puncture holes in bacteria to destroy it) |
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What is the difference between affinity and avidity? |
-affinity refers to the strength with which a single antigen binding site of an Ig isotype binds antigen -avidity refers to the combined affinities of the entire isotype (therefore IgM, with 10 antigen binding sites, often has a very high avidity for its antigen) |
