Antibody Repertoire and Gene Expression Profile: Implications for Different Developmental and Functional Traits of Splenic

In L2 mice, a high expression level of the transgenic 2315 L chain results in nearly complete exclusion of endogenous L chains and a predominance of B-1a cells. In this study, we show that splenic and peritoneal B-1a cells differ considerably in their Ab repertoire and gene expression profile. Splenic B-1a cells exhibit a more diversified repertoire under L chain limitation. Despite oligoclonal overlaps between both B-1a compartments, some B cell receptor specificities are clearly restricted to the peritoneum. The capacity of peritoneal B-1a cells to enter the splenic B-1a compartment was found to be very limited. Gene expression profiling revealed genes up-regulated in splenic B-1a cells that are involved in mediating specialized first-line-of-defense effector functions and interaction with T cells. Thus, splenic and peritoneal B-1a cells differ not only in their developmental program but also in functional properties. The Journal of Immunology, 2003, 171: 1192–1201. T he mature preimmune B cell compartment of adult miceconsists of at least four subpopulations, each of whichexhibits specific developmental and functional character-istics: recirculating follicular B cells (or B-2 cells) representing the major B cell subpopulation of lymphoid follicles, marginal zone (MZ)4 B cells enriched in the MZ surrounding the splenic lym-phoid follicles, and B-1 lymphocytes, which can be subdivided into B-1a cells expressing CD5 and the CD5 B-1b sister popu-lation (1, 2)