V-gene usage and N-region insertions in B-1a, B-1b and conventional B cells.

The adult B-1a cell repertoire shows both substantial diversity and characteristic features. Recent studies using PCR to amplify variable-region transcripts from single, FACS-sorted B cells illuminate this apparent dichotomy. Although there is substantial diversity in the number of different rearrangements, characteristic patterns of VH-gene usage, combined with low use of N-region insertions when compared with conventional B cells, distinguish the B-1a repertoire. B-1b cells also have characteristic features of their own. These results are discussed in the context of key developmental and regulatory events which shape the B-1a and B-1b repertoires.