SUPPRESSION OF B-CELL DIFFERENTIATION BY LIGATION OF MEMBRANE-BOUND IGM

Using B cells from the transgenic mouse line B6-Sp6 and control litter mates, stimulated by lipopolysaccharide (LPS) under novel culture cond itions that provide for the response of all B cells, we show here that specific ligation of the surface IgM molecules always results in inhi bition of terminal differentiation and immunoglobulin secretion by act ivated cells, regardless of the ligand. Thus, monoclonal antibodies to (a) the CH region of Ig (anti-mu and anti-allotype), (b) the Cchi reg ion, (c) the V region (anti-idiotype) of surface IgM, as well as (d) m ultivalent antigen (2,4,6-trinitrophenyl-bovine serum albumin), all sh ow similar effects and dose-response curves. IgD-negative transgenic B cells are equally sensitive to IgM ligation-dependent inhibition, as control (IgD-positive) B cells. The allotype specificity of this inhib ition, assessed by using anti-mu allotype reagents to inhibit and assa y the responses, suggests that B cells expressing transgenic or endoge nous IgM in transgenic B6-Sp6 mice are largely independent populations . These observations establish that anti-IgM antibodies in conjunction with appropriate LPS stimulation, provide a universal model system fo r functional characterization of B cell responses.