Implications for the role of cognate interactions in in vitro human B cell activation by Staphylococcus aureus Cowan I and pokeweed mitogen.
Human B cell-triggering mechanisms were investigated using the polyclonal activators Staphylococcus aureus Cowan I (SAC) and pokeweed mitogen (PWM). When the cultures of B cells, T cells, and monocytes were stimulated for 5 d by SAC or PWM, B cells could be activated by both mitogens to proliferate and secrete Ig. Even when T cells were substituted by T cell-derived soluble factors, SAC-stimulated B cells could differentiate into Ig-secreting cells. In contrast, interactions of B and T cells for at least the first 6 h of culture were necessary for the B cell triggering by PWM. Experiments that allow a more precise delineation of the B cell-triggering mechanisms by PWM demonstrated that interactions of B cells with T4+ but not T8+ cells are required for the B cell triggering; anti-Ia or anti-T4 antibody can block this triggering; in contrast, anti-T3 or anti-T8 antibody do not exert any effects on the B cell triggering. However, all these monoclonal antibodies could not modulate the ability of B cells that had been already activated by PWM to respond to T cell-derived factors. These data suggest that SAC can directly activate B cells, while cognate interactions between Ia-like antigens on B cells and T4+ cells are essential for B cell triggering by PWM. Furthermore, once B cells are triggered, they will proliferate, differentiate, and secrete Ig in response to T cell-derived factors; Ia-like antigens or T cell differentiation antigens may not be involved in the processes in this cascade.
D000911:Antibodies, Monoclonal / Q000502:physiology; D001402:B-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D006801:Humans; D007136:Immunoglobulins / Q000096:biosynthesis; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D011043:Pokeweed Mitogens / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000276:immunology*; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology; D013997:Time Factors
D000911:Antibodies, Monoclonal; D007136:Immunoglobulins; D011043:Pokeweed Mitogens