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16 Cards in this Set
- Front
- Back
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Antibodies/immunoglobulins(Igs) are synthesized by B cells and perform what general functions?
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Antibodies facilitate phagocytosis by opsonization and neutralize toxins and viruses.
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What is Isotype?
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Antibodies that differ by constant regions(IgG, IgA, IgM, IgE, IgD)
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What is idiotype?
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Antibodies that differ by hypervariable region.
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What is meant by allotype?
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Antibodies that differ among individuals due to polymorphisms(more than 2 alleles) in heavy and light chains.
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A simple Y-shaped antibody is composed of a two heavy chains and 2 light chains(named according to molecular weight) connected by disulfide bonds. Each chain is composed of variable and constant regions. What is the function of these regions?
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Variable regions of both heavy and light chains mediate antigen binding. The constant regions of the heavy chains serve effector functions binding to receptors on immune cells(IgE can attach to mast cell receptors, IgG can attach to NK cells and activating complement.
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What are hypervariable regions?
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Three sequences od amino acids with profound variability located within the variable regions of both heavy and light chains. They are responsible for the specificity of antibodies.
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How many heavy chain constant domains(constituents of constant regions) are present on IgG, IgA, IgM and IgE?
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IgG and IgA have three while IgM and IgE have 4(all light chains have one constant domain).
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What are the Fab and Fc fragments? Which one is at theamino terminus and which one is at the carboxyl terminus/ Whatseparates Fab and Fc fragments?
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Fab fragment is the part of an antibody that contains the antigen binding sites located at the amino terminus. The Fc fragment, located at the carboxyl terminus, is composed of heavy chain constant domains and serves effector functions. Fab and Fc are separated by the hinge region.
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What is the function of the hinge region of the immunoglobulin/
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Allows flexibility within an antibody resulting in a broader array of binding conformations.
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What does the identification of the presence of both kappa and lambda light chains suggest about a sample of antibody?
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The antibodies are not monoclonal. Antibodies have either kappa or lambda light chains, but never both. Thus, the presence of both implies that there must be atleast 2 different types of antibodies in the sample.
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What is the function of the J chain on IgA and IgM isotypes?
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The J chain plays a critical role in the stabilization of the multimeric forms of IgA and IgM. In its absence, all isotypes would be monomeric.
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What is affinity?
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Binding strength at a single antibody variable region and antigen epitope.
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What is valency?
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Number of sites at which an antibody binds an antigen.
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What is avidity?
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Overall strength of an interaction between an antibody and antigen, determined by both affinity and valency.
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What isotype has the highest avidity and why?
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IgM because it has 10 binding sites(valence of ten).
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What isotypes of antibodies allow for B cells to acheive antigen presentation?
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The membrane bound form of IgM and IgD (which only exists as a membrane bound form) function to recognize and allow endocytosis od antigens within the naive B cell, allowing them to subsequently be presented to T cells. This constitutes the recognition phase of humoral immune responses.
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