Comparison of V kappa gene family expression in adult and fetal B cells.

The functional B cell repertoires from adult and fetal mice were compared by examining V kappa gene family expression in individual cells. In addition, because little is known about the relative use of the various V kappa gene families in an immune response, adult B cells from several different strains of mice were analyzed. This was accomplished by stimulating B cells with the polyclonal activator, LPS. Activated cells were then analyzed for V kappa gene family expression at the single cell level by in situ hybridization using radiolabeled V kappa gene probes. It was found that all V kappa gene families tested were represented in the LPS-induced adult repertoire with V kappa 1, V kappa 4,5 and V kappa 19 being expressed to the largest degree in all strains tested. The LPS-induced adult V kappa gene family repertoire was then compared to the fetal repertoire and some differences were observed. In particular, a lower proportion of fetal B cells expressed V kappa 1 and a higher proportion of fetal B cells expressed V kappa 4,5 and V kappa 10. Importantly, compared with the adult response there was no evidence in the fetal response for an increased expression of V kappa 21, the family that maps closest to J kappa,C kappa. This is in contrast to what has been shown previously with H chain V region exons in which there was a clear preference for the VH gene families that mapped closest to DH.