Signal transmission through the B cell-specific MB-1 molecule at the pre-B cell stage

Abstract

Specific binding of antigens to the surface immunoglobulln M (slgM) triggers B cells with several biochemical events Involved in receptor-mediated signal transmission for proliferation and differentiation into antibody-producing cells. Recent studies with the Digitonin lysis method identified the slgM-assoclated component, IgM-α (B34)/lg-β, as the possible candidate for the transducer molecule(s) In the immunoglobulln receptor-mediated signal transmission. The 34 kdprotein (B34 or IgM-α) of this component Is suggested to be encoded by the B cell-specific mb-1 gene. We prepared monoclonal antibodies which recognize the mb-1 gene product (MB-1) and studied the functional role of MB-1 In the signal transmission In B lineage cells. Using murine pre-B lymphoma cells (18–81 and 70Z/3), we demonstrated the early phase increase of the Intracellular [Ca²⁺] concentration and the subsequent inhibition of the proliferation by the monoclonal anti-MB-1 antibody (11–18–5). These results clearly demonstrate signal transmission through the surface MB-1 molecule on B lineage lymphomas. This MB-1-mediated signal transmission in pre-B cell lines would suggest an alternative function of MB-1 acting at the pre-B cell stage.