A PREMATURELY EXPRESSED IG-KAPPA TRANSGENE, BUT NOT A V-KAPPA-J-KAPPAGENE SEGMENT TARGETED INTO THE IG-KAPPA LOCUS, CAN RESCUE B-CELL DEVELOPMENT IN LAMBDA-5-DEFICIENT MICE

We generated surrogate light chain (SLC)-deficient mice carrying eithe r a V kappa J kappa-C kappa transgene under the control of the kappa p romoter and intron enhancer or a V kappa J kappa gene segment targeted into its physiological position. Efficient rescue of B cell developme nt was seen in the former and partial rescue in the latter. This diffe rence corresponded to a developmentally earlier onset of kappa chain e xpression from the conventional than from the targeted transgene. Thus , a kappa chain can substitute for SLC in development. However, mechan isms controlling gene expression in addition to gene rearrangements ap pear to restrict kappa chain expression largely to a cellular compartm ent into which mu chain-expressing B cell progenitors are selected wit h the help of the SLC.