Identifying the cellular interactions required for diversification of the primary antibody repertoire in rabbit GALT (P6101)

Abstract

Abstract Rabbits generate an initial antibody repertoire of limited diversity due to preferential use of the 3’-most VH gene segment during V-D-J gene rearrangement. Around one week of age, rabbit B cells begin diversifying this antibody repertoire in gut-associated lymphoid tissue (GALT), by mutating their V-D-J genes in response to antigen-independent signals acquired from intestinal commensals. To identify the cell-cell and cell-microbe interactions required for V-D-J gene diversification, we examined B cell expression levels of four chemokine receptors that mediate homing to important sites within GALT. We stained the chemokine receptors CXCR4, CCR6, CXCR5 and CCR7 on appendix B cells from two- to eight-day-old rabbits with fluorescence-labeled antibodies or chemokine-Ig fusion proteins and analyzed them by flow cytometry. The changes in chemokine receptor expression we observed during the first week of life suggest that, after entering appendix follicles, B cells first home to the follicle-associated epithelium, where they likely encounter commensal bacteria sampled from the intestinal microbiota. B cells then home sequentially to the follicular dendritic cell network, the T cell area and finally to the basal region of the follicle, where they proliferate and diversify their V-D-J genes to generate the primary antibody repertoire.