Signal transduction via MHC class II antigens on B lymphocytes

The role of the MHC class II antigens in the activation of resting human B lymphocytes (B-Go) was examined with respect to both early and late events in the activation process. The (Ca2+)i induced by anti-IgM was enhanced in the presence of, or following pre-incubation with, an anti-MHC class II DR antibody (D1.12). Pre-incubation with a sepharose conjugated antibody (Seph.-D1.12) augmented the proliferation of B-Go in response to a sub-optimal concentration of anti-IgM. The 2D PAGE profile of B-Go differed from that of in vivo activated B lymphocytes. The 2D PAGE profile of B-Go activated by Seph.-D1.12 was not identical to the profile of B-Go activated by either anti-IgM or PMA. These data suggest that the activation of B-Go via the class II antigens shares part of the pathway of anti-IgM induced activation but does not follow an identical pathway.