Rabbit IgH sequences in appendix germinal centers: VH diversification by gene conversion-like and hypermutation mechanisms

Although the rabbit IgH locus contains approximately 100 VH genes, the majority of B cells rearrange VH1. To produce a primary repertoire containing a sufficient number of protective antibodies, rearranged VH 1-DH-JH sequences may diversify within rabbit B cells in an organ that functions like a chicken bursa, sheep ileal Peyer's patch, or both. It was suggested many years ago that the rabbit appendix could be a bursal equivalent. To reexamine this possibility, we analyzed rearranged heavy chain variable region sequences in B cells from light and dark zones of appendix germinal centers from 6-week-old rabbits. Our findings indicate that antibody diversification occurs by gene conversion-like and somatic hypermutation mechanisms in appendix germinal centers of young rabbits.