V lambda-J lambda rearrangements are restricted within a V-J-C recombination unit in the mouse.

The murine lambda gene locus is organized as follows: V lambda 2-V lambda x-J lambda 2C lambda 2-psi J lambda 4C lambda 4-V lambda 1-J lambda 3C lambda 3-J lambda 1C lambda 1 where all segments have the same transcriptional orientation. The combinatorial process of gene recombination should allow the generation of eight distinct immunoglobulin light chains. We have therefore investigated the probability of obtaining such chains among the mature lambda B cell repertoire. We analyze serum lambda immunoglobulins and lambda B cell clones induced by treatment with rabbit anti-lambda antibodies coupled to LPS. Confirming previous data obtained by others, our results indicate that the rearrangements of lambda segments take place within each V lambda-J lambda-C lambda cluster, thereby defining a unit of recombination. Our results also provide no evidence for the use of undescribed segments as has been recently suggested by the finding of the V lambda x segment.