Mechanistic and selective constraints act on the establishment of V lambda J lambda junctions in the B cell repertoire.

Only four different subtypes of lambda Ig chains have been described in the mouse: lambda 1, lambda 2(V2), lambda 2(Vx), and lambda 3. These chains are encoded by gene segments all sequenced and well localized in chromosome 16. Although the lambda Ig system is both simple and well characterized, no exhaustive analysis has been done concerning V lambda J lambda junctions in nonintentionally stimulated B cells. To get an insight into the lambda B cell repertoire, we analyzed a large number of V lambda J lambda rearrangements isolated from spleen mRNA or genomic DNA of unimmunized adult BALB/c mice. By PCR amplification, more than 160 clones were obtained covering all V lambda J lambda recombinations. Simple recombinations of trimmed gene segments explain most sequences. Certain junctions have been found to be prevalent in each subtype, and an analysis of V lambda J lambda recombination sites shows that the splenic lambda repertoire can result from both differential efficiencies of rearrangement and selective processes.