BIASED VH GENE-EXPRESSION IN MURINE CD5 B-CELLS RESULTS FROM AGE-DEPENDENT CELLULAR-SELECTION

Flow cytometry-purified, peritoneal and splenic CD5+ and CD5- B cells from neonatal and adult C57BL/6 mice were studied for expression of V(H) and V-kappa-gene families in RNA colony blot assays, and for frequencies of clones secreting antibodies to bromelain-treated mouse red blood cells (BrMRBC), single-stranded DNA, trimethyl ammonium and bovine-gamma-globulin, by limiting dilution. The results show few overall differences between the two B cell subsets, which both manifest ontogenic D-proximal V(H) preferences that are lost with age. Biased V(H)11 expression in CD5 B cells is high in adult peritoneum and spleen but absent in newborns. It only partly correlates with the selection of anti-BrMRBC reactivity, which is considerably higher in peritoneum than in spleen. No particular V-kappa-bias was observed in any of the populations studied with the possible exception of V-kappa-22 in peritoneal CD5+ B cells. We conclude that the antibody repertoire expressed by peritoneal CD5+ B cells of adult mice is not the result of a genetic program, but rather the consequence of local, age-dependent cellular selection mechanisms.