Four of five RAG-expressing JC kappa(-/-) small pre-Bll cells have no L chain gene rearrangements: Detection by high-efficiency single cell PCR

Single cell PCR assays have been further developed that detect over 80% of all V kappa J kappa V kappa RS, and V lambda J lambda rearrangements at eff iciencies between 70% and 90%. These IgL chain gene rearrangement assays we re used with small pre-BII cells that develop in comparably high numbers in the bone marrow of wild-type, C kappa-deficient, and JC kappa-deficient ho mozygous and heterozygous mice. In all of these mice, only 15%-25% of all s mall pre-BII cells carry V lambda J lambda rearrangements. These results co nfirm that lambda L chain gene rearrangements occur independently of kappa L chain gene rearrangement and expression. They also show that a large part of the small pre-BII cells that express the rearrangement machinery can de velop without IgL chain gene rearrangements.