3 - 3.3 Answer #3: Evolution of affinity It is in...

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3.3 Answer #3: Evolution of affinity It is in considering the third and last question -- how antibody affinity increases during an immune response -- that we come to the raison d'etre of this article, for investigations have clearly shown that the mechanism of the affinity rise that progressively improves the efficiency of antibody function is random mutation and selection. The evidence comes from analysis of several immune responses in inbred strains of mice, which all paint the same general picture (Wysocki et al. Proc Natl Acad Sci USA 83:1847, 1986; Griffiths et al. Nature 312:271, 1984). The responses are analyzed by determining the antibody gene structures from B lymphocytes taken before and at different times after immunization with an antigen (see Figure 3). Before immunization and during the first few days after immunization, any antigen-binding cells express antibody gene sequences derived from unaltered combinations of the germline elements described above. But beginning after about a week, the sequences clearly show evidence of mutation: many sequences are different from the germline elements from which they were constructed. Because the animals in these experiments are inbred, all the individuals are like identical twins, born with identical DNA sequences in all their genes. In particular, the sequences of their germline variable region gene elements are all known, so that any immunoglobulin sequences differing from the corresponding germline genes must be the result of mutations that
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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.

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3 - 3.3 Answer #3: Evolution of affinity It is in...

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