kappa gene diversity among the clonal progeny of pre-B lymphocytes.

Some clonal pre-B cell lines, when transformed by Abelson murine leukemia virus, are able to rearrange and express kappa light chain genes. We have analyzed the light chains expressed in sets of early B-cell subclones derived from two pre-B cell clones. Each subclone makes an indistinguishable mu heavy chain, while the kappa gene rearrangements and proteins synthesized were distinct. All members of one set of subclones expressed a V kappa 21 kappa light chain. Only one of the members of the other two sets of subclones expressed V kappa 21. Thus, a single pre-B-cell clone can select a kappa variable region from more than one family. In each subclone of the set that expressed V kappa 21 light chain the same member appears to be used. The differences detected in the expressed proteins can best be explained by primary sequence alterations in the rearranged V kappa 21 segment. These sequence alterations have resulted in a restriction site polymorphism in the expressed V kappa 21 gene and charge and size differences in the expressed proteins. These data suggest that diversification of kappa light chains can occur at the pre-B- to early B-cell stage of development.