Selection for S107-V11 gene expression by peritoneal B cells in adult mice

Peritoneal B-1 cells in adult mice express a restricted repertoire of V genes. To determine the basis for the nonrandom expression of one VH gene (the V11 gene in the S107 family), and to determine if this gene is nonrandomly expressed early in development, we amplified rearranged S107 genes in adult and neonatal tissues taken from B10.H-2aH-4bp/Wts (2a4b) mice. In adult peritoneal B cells, the S107-V11 gene was found to be productively rearranged up to five times more frequently than V1, another member of the S107 VH gene family. This did not occur in adult spleen, or in neonatal spleen or liver. In these three tissues the productive S107-V11/V1 rearrangement ratios ranged from 0.5 to 0.9. This difference suggests that S107-V11-expressing peritoneal B cells in adult mice have been selected and clonally expanded. Clonal expansion is further suggested by the differing ratios of productive to nonproductive rearrangements. In adult peritoneal B cells, the S107-V11 productive/non-productive ratio is higher than that of V1, consistent with the clonal expansion of S107-V11-expressing cells but not of V1-expressing cells. Analysis of the VHDJH junctional sequences in the productive S107-V11 rearrangements reveals that there are no predominant restrictions in the lengths or sequences of the third complementarity determining regions (CDR3). Selection is therefore independent of CDR3 and so must be based on germline-encoded portions of the S107-V11 region.