PHENOTYPIC CONVERGENCE AND DIVERGENCE OF SURFACE-IMMUNOGLOBULIN AND CD40 SIGNALS

Both anti-CD40 antibodies and anti-immunoglobulin (Ig) coupled to Seph arose induced proliferation of resting B cells and suppressed lipopoly saccharide (LPS)-induced B-cell differentiation to immunoglobulin secr etion at comparable levels determined with the plaque-forming assay an d Ig RNA steady state levels. Anti-CD40 antibodies also increased the proliferation of B cells stimulated by T helper cells bl vitro while s uppressing their differentiation to Ig secretion. Further, B cells pre activated by anti-Ig, anti-CD40 or a combination of the two mitogens c ould be restimulated by anti-CD40 but not by anti-Ig antibodies. Pheno typic divergence of Ig and CD40 signals regarding surface expression o f activation markers was observed. Restimulation of anti-Ig-or anti-CD 40-prestimulated cells with anti-Ig induced apoptosis whereas apoptosi s could be inhibited when cells were recultivated with anti-CD40.