Examination of the in vitro V kappa gene rearrangements of murine adult bone marrow-derived pre-B cell lines reveals that 21 of 25 (84%) cell lines have rearranged a member of the V kappa 4 family. In contrast, analysis of two V kappa cDNA libraries prepared from LPS-stimulated adult spleen cells indicates that only 17% of the Ig kappa cDNAs contain sequences belonging to the V kappa 4 gene family. Half of the pre-B cell lines examined also share an 8-kbp BamHI reciprocal product (rp). However, these rp do not involve the same V kappa gene, indicating that conserved BamHI sites exist 3' of some V kappa genes. This rp is also readily detected in DNA from normal adult spleen cells, suggesting that the in vitro rearrangements examined in this study are representative of kappa rearrangements that occur in vivo. We suggest that, unlike the diverse V kappa repertoire expressed by mature B cells, the germline V kappa segments involved in initial rearrangements of the Ig kappa locus are highly restricted, and that an initial V kappa 4 rearrangement is probably followed by other, more random recombination events.

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