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 i n 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 wel l characterized, no exhaustive analysis has been done concerning V(lam bda)J(lambda) junctions in nonintentionally stimulated B cells. To get an insight into the lambda B cell repertoire, we analyzed a large num ber of V(lambda)J(lambda) rearrangements isolated from spleen mRNA or genomic DNA of unimmunized adult BALB/c mice. By PCR amplification, mo re than 160 clones were obtained covering all V(lambda)J(lambda) recom binations. 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 sho ws that the splenic lambda repertoire can result from both differentia l efficiencies of rearrangement and selective processes.