Monoclonal antibodies against HLA-DR antigens replace T helper cells in activation of B lymphocytes.
In the presence but not in the absence of pokeweed mitogen (PWM), monoclonal antibodies against HLA-DR antigens 147 and 164 helped highly purified B lymphocytes to proliferate and mature to Ig-secreting cells. In contrast, neither anti-DR antibody 231 nor the UCHT1 monoclonal anti-human T cell antibody (both of the same isotype as the 147 and 164 anti-DR antibodies) exhibited any helper activity on B cells. B cells pulsed with PWM and subsequently cultured in the presence of anti-DR antibody 147 or 164 proliferated and secreted Ig, whereas B cells that first were pulsed with antibody 147 or 164 and then incubated with PWM did not. PWM alone did not induce any of these responses on purified B cells. Also, antibodies 147 and 164 significantly increased the number of Ig-secreting cells obtained from the WT51 Epstein-Barr virus-transformed B-cell line. Anti-DR antibody 231 inhibited the helper activity on WT51 cells mediated by anti-DR antibody 164. Finally, anti-DR antibodies 147 and 164 assisted B cells from the spleen of athymic nu/nu mice (which bear I-E-encoded products) to produce IgM antibodies against sheep erythrocytes. However, these antibodies had no effect on mouse B cells which do not express on their surface I-E-encoded Ia antigens. Taken collectively, these findings suggest that the structures detected by anti-DR antibodies 147 and 164 on B lymphocytes function as acceptors/transducers of T-cell-derived helper signals.
D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D001402:B-Lymphocytes / Q000276:immunology*; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D011043:Pokeweed Mitogens; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D011043:Pokeweed Mitogens