Antibodies help to defend the body against infections. They work by binding foreign chemical markers called antigens. The diversity of antigens is staggering, and cells that make them (B lymphocytes) have the ability to undergo somatic recombination (programed changes to DNA) to increase the variability of antibodies. Of specific importance is the variable domain:



In the above diagram, look at the Variable Domain of the Light Chain (VL). Notice 3 areas drawn in red, and referred to as the Loops that Bind Antigens. These are the areas where Somatic Recombination can change the nucleotides present in the gene. If I change the nucleotides (as with hemoglobin above), I can change the amino acids in the primary sequence. Explain how changing the primary sequence in these loop regions can change the binding affinity of an antibody to an antigen, and why this is beneficial to the body.

This is not for a grade. Its just a discussion and I need a really detailed brief understanding of this because I have a test coming up soon. Much help would be appreciated !!!!

By changing the variable domain of a light chain, primarily the area that bind the antigen, you change its binding affinity to that said antigen. You do not know if you make the antibody more or less selective for the desired substrate. By changing the amino acid sequence you will change the 3-D structure of these "loops" as well as change the charge at that point (different amino acids have more/less + or - on them). This is beneficial because it allows the body to produce more both more selective antibodies and also "new" antibodies if the binding site on the antigen changes. One example would be the flu virus constantly changing its antigen site. Allowing for slight change in the binding site allows for the body to protect itself from it. It also is useful for 'new' viruses

hopefully this is all right, kinda in a hurry getting rdy for work

This post was edited by cialda on Sep 9 2013 07:04am