A mechanism by which activated B cells can generate antibodies of increased specificity and with improved antigen binding over the course of an adaptive immune response. Special adaptations of these cells give rise to a relatively high rate of enzyme-induced base changes to the DNA of genes encoding the variable regions of both heavy and light chains of the antibody molecules. Such mutations are confined to clones of B cells generated by a T-cell-mediated response to the presence of specific antigen (see helper T cell) and do not affect germ-line cells, so cannot be inherited. Over the course of several weeks, B cells that accumulate beneficial mutations producing better antigen binding receive signals that promote their proliferation, whereas their counterparts with deleterious mutations can no longer bind antigen and die. Consequently, the efficiency of antigen binding of the B-cell population, and hence the overall effectiveness of the antibody response, increase over time. Compare somatic recombination.
Subjects: Biological Sciences.