Development of the antibody repertoire in rabbit: gut-associated lymphoid tissue, microbes, and selection.

Rabbits generate their antibody repertoire in three stages. First, a neonatal repertoire is generated by B lymphopoiesis in fetal liver and bone marrow and is limited by preferential V(H) gene segment usage. Between 4 and 8 weeks after birth a complex primary antibody repertoire is developed by somatically diversifying the neonatal repertoire through somatic hypermutation and a somatic gene conversion-like mechanism in gut-associated lymphoid tissue (GALT). In rabbits, unlike other species, the development of the primary antibody repertoire through somatic diversification of Ig genes appears to be dependent on intestinal microbial flora. The primary antibody repertoire is subsequently modified during antigen-dependent immune responses in which VDJ genes further diversify both by somatic hypermutation and by a gene conversion-like mechanism (the secondary repertoire). During the various stages of development, the antibody repertoire is modified and shaped by selective processes. In this review, we discuss the roles of GALT, microbes, and B-cell selection in generating antibody diversity in rabbits.