Structure, Control of Expression and Putative Function of the PreB Cell-Specific Genes V_preB and λ₅

Abstract

When mouse B lymphocytes develop from progenitors and precursors either during embryogenesis in embryonal blood and fetal liver or during adulthood in bone marrow, Ig gene segments of H and L chain loci are rearranged in temporal order to form complete H and L chain genes from which Ig can be expressed on the surface of B lineage cells (Tonegawa 1983). In fetal liver between day 13 and 16 of gestation B lineage progenitors are induced by contact with stromal cells to four critical divisions in which these Ig gene rearrangements take place (Melchers 1977a, 1977b; Melchers et al. 1975; Paige et al. 1984; Kincade et al. 1981; Whitlock et al. 1985; Dorshkind et al. 1986; Witte et al. 1987; Pietrangeli et al. 1988; Kinashi et al. 1988; Palacios et al. 1989; Kincade et al. 1989; Gisler et al. 1987; Palacios et al. 1984; Palacios and Steinmetz 1985; Palacios et al. 1987; Namen et al. 1988; Melchers et al. 1989). Once preB cells express Ig on their surface they mature between day 16 and 19 of gestation to surface Ig positive mitogen- and antigen-sensitive B cells without much proliferation (Melchers et al. 1989; Osmond 1986). The molecular mechanisms which control the development from progenitors to mature B cells, the critical cell divisions and the Ig gene rearrangements are largely unknown.