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20 Cards in this Set
- Front
- Back
Why is clonal selection important?
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It is the central mechanism for how the adaptive immune system works for both B-cells and T-cells. It is the process by which the huge repertoire of B cells and T-cells with differing antigen specificities are generated.
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what is the general structure of an antibody?
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Ig is composed of two identical light chains and two identical heavy chain polypeptides with 2 and 4 intra-chain disulide bonds, respectively. Each chain can be differentially glycoslated. The N-terminal region is the variable region and the C-terminal region is the constant region.
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What are the primary functions of antibodies and where are these functions accomplished on the molecule?
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They must specifically recognize antigen. This occurs at the end of the molecule at the variable regions containing two antigen-binding regions. Antibodies must also eliminate antigen. This function resides in the C terminus of the constant region of the heavy chain. Only one antigen-elimination region
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What does Papain do?
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Papain cleaves above the disulfide bond that keeps the heavy chian and constant regions together. You get two Fab molecules (fragment antigen binding) and one Fc (the antigen elimination region).
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What does Pepsin do?
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Pepsin cleaves several sites, pretty much destroying the heavy chain constant region so you don't have Fc. You still get a Fab with both antigen binding regions together.
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Describe the constant domains in the antibody.
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2 constant domains in the light chain and 4 or more in the heavy chain. 7 antiparallel beta pleated sheets stabilized by disulfide bonds.
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Describe the variable domains in the antibody.
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Less regular than the Ig constant domains. Same 7 anitparallel beta pleated sheets stabilized by disulfide bonds.
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What are hypervariable regions of the antibody and what do they do?
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The HV regions which are also known as CDRs (complementarity determining regions) determine the anting recognition specificity. The HV regions occur in loops between the B-pleated sheets.
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What type of interaction do antigens have with the antigen binding regions of antibodies?
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Non-covalent, weak, low energy interactions such as electrostatic forces, hydrogen bonds, Van der Waals forces, and hydrophobic forces.
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How are the elimination properties of antibodies determined?
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The Fc region of the antibody determines the antigen elimination properties of antibodies.
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How many different classes of of heavy chain constant regions are there?
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5 different classes of heavy chain constant regions. The 5 classes are IgG, IgM, IgD, IgA, IgE
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Are the structure of all the isotypes of the heavy chain constant region the same?
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No. The IgG, IgD, IgA have 2 Ig domains in the Fc portion while IgM and IgE have 3 Ig domains. In additon, IgG, IgD, IgA have a hinge which is encoded by an exon.
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What is an allotype?
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polymorphism in a particular individual's Ig gene
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What is an idiotype?
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unique antigen recognition site at the end of the variable region that is comprised of both heavy and light chains
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What is an epitope?
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molecular structure on the antigen that is recognized
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Describe the structure of the TCR
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A clonotypic transmembrane receptor on T-lymphocytes. Look like Fab fragments which have two chains held together by one intra-strand disulfide bond with various glycosylation sites. The C region of the alpha chain has 4 beta-pleated sheets
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What is the job of the TCR?
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The job of the TCR is to recognize antigen presented by MHC molecules. The TCR recognition occurs at the loops between the beta pleated sheets.
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How is diversity generated in the TCR and Ig?
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somatic recombination of the 3 loci for the TCR (beta chain, alpha chain, and gamma chain) and the 3 loci for the Ig polypeptide (1 heavy chain and 2 light chain (kappa, lambda))
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How many segments encode for the light chain?
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For the light chain each gene is encoded by V, J, C segments. The variable region is encoded by the V and J segments of the gene. The constant region is encoded by the C segment.
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How many segments enode for the heavy chain?
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For the heavy chain the variable region is encoded by V, D, and J segments. Most of the variable region of the heavy chain is encoded by the V gene segment.
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