Figure 2.

[A] Classical models of somatic hypermutation conceive of rapid generation of variants in the activated germinal center followed by a severe down-selection of number of variants, resulting in selection of only the clones with the most avidly binding B cell receptors for survival. [B] Newer repertoire studies using large-scale sequence analysis reveal that human B cell repertoires retain large number of variants with diverse numbers of point mutations within clones, even in the peripheral blood.