Four of five RAG-expressing JCκ-/- 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 efficiencies between 70% and 90%. These IgL chain gene rearrangement assays were 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 homozygous and heterozygous mice. In all of these mice, only 15%-25% of all small pre-BII cells carry V lambda J lambda rearrangements. These results confirm 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 develop without IgL chain gene rearrangements.