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20 Cards in this Set

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  • Back
Why is clonal selection important?
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.
what is the general structure of an antibody?
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.
What are the primary functions of antibodies and where are these functions accomplished on the molecule?
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
What does Papain do?
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).
What does Pepsin do?
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.
Describe the constant domains in the antibody.
2 constant domains in the light chain and 4 or more in the heavy chain. 7 antiparallel beta pleated sheets stabilized by disulfide bonds.
Describe the variable domains in the antibody.
Less regular than the Ig constant domains. Same 7 anitparallel beta pleated sheets stabilized by disulfide bonds.
What are hypervariable regions of the antibody and what do they do?
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.
What type of interaction do antigens have with the antigen binding regions of antibodies?
Non-covalent, weak, low energy interactions such as electrostatic forces, hydrogen bonds, Van der Waals forces, and hydrophobic forces.
How are the elimination properties of antibodies determined?
The Fc region of the antibody determines the antigen elimination properties of antibodies.
How many different classes of of heavy chain constant regions are there?
5 different classes of heavy chain constant regions. The 5 classes are IgG, IgM, IgD, IgA, IgE
Are the structure of all the isotypes of the heavy chain constant region the same?
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.
What is an allotype?
polymorphism in a particular individual's Ig gene
What is an idiotype?
unique antigen recognition site at the end of the variable region that is comprised of both heavy and light chains
What is an epitope?
molecular structure on the antigen that is recognized
Describe the structure of the TCR
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
What is the job of the TCR?
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.
How is diversity generated in the TCR and Ig?
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))
How many segments encode for the light chain?
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.
How many segments enode for the heavy chain?
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.