The Evolution of Improved Fitness Evolution of antibody sequences The model deduced from these findings provides an unambiguous biological example of the power of random mutations and selection. (The current model as understood by molecular immunologists is slightly more complex than described below, but does not differ in any features relevant to the logic of this essay.) When antigen enters the body, it triggers a small number of B lymphocytes -- namely those whose surface antibody can bind the antigen -- to multiply and secrete antibody. These early responding antibody sequences are made of assembled germline gene elements in unmutated form, and frequently have low affinity. Furthermore, these antibodies were not "designed" to bind the antigen; they were proteins that happened to pre-exist in the body before any exposure to the novel challenge with antigen. As the immune response continues, the antigen-activated B cells move to germinal centers. Hypermutation begins, and starts generating antibodies with altered structures. The hypermutation mechanism acts randomly
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This note was uploaded on 11/14/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.