Fluorescence activated cell sorter analysis of murine B cell development.

Three subpopulations of surface immunoglobulin positive B cells were defined using monoclonal antibodies directed against IgM and IgD antigenic determinants and 2-color fluorescence activated cell sorter analysis: cells with a high density of sIgM and lacking sIgD (M++D-); cells with slightly less sIgM and dully positive for sIgD (M++D+), and cells with a low density of sIgM but brightly staining with anti-IgD (M+D+). In the spleen of two-week-old animals the M++D- cells are the more numerous. Their frequency declines during development in favor of the adult M+D+ cells. Because the densities of sIgM and sIgD on M+D+ cells are positively correlated it is hypothesized that immature M++D- cells first lose their sIgM and then reaquire sIgM together with sIgD.