Evidence that Lyb-2 is critical to specific activation of B cells before they become responsive to T cell and other signals.
The generation of plaque-forming cells (PFC) to T-dependent antigen, but not to T-independent antigen, is reduced in vitro by Lyb-2 antibody. Monoclonal Lyb-2 antibody, added to Mishell-Dutton cultures within the first 2 d, but not later, greatly reduces the generation of alpha-sheep erythrocyte (SRBC) PFC from T-depleted spleen cells whether help is provided in the form of intact T cells or as soluble factors contained in mixed lymphocyte culture (MLC) supernatants. Generation of alpha-SRBC PFC from purified B cells, assisted by soluble factors in MLC and macrophage (P388D.1 cell) supernatants, is similarly reduced by Lyb-2 antibody. The initial 2-d period, during which cultures are diminishingly sensitive to reduction of PFC generation by Lyb-2 antibody, is not affected by the time at which such soluble factors are added. Thus, Lyb-2 cell surface molecules evidently do not function as receptors for these differentiative signals. Reduction of PFC generation by Lyb-2 antibody is antigen dependent in the sense that reduction of the PFC response to one antigen (SRBC) does not affect subsequent generation of PFC to a second antigen (horse erythrocytes) from the same cell population. These findings accord with the view that the Lyb-2 molecule participates in a B cell differentiative phase, probably proliferative, which begins with binding of antigen and precedes the phase in which B cells become fully receptive to signals from T and other cells.
D000818:Animals; D000906:Antibodies; D000921:Antibody-Producing Cells / Q000276:immunology; D000950:Antigens, Ly / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D001667:Binding, Competitive; D000939:Epitopes; D006736:Horses; D008213:Lymphocyte Activation; D007959:Lymphocyte Culture Test, Mixed; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D012756:Sheep; D013601:T-Lymphocytes / Q000276:immunology*
D000906:Antibodies; D000950:Antigens, Ly; D000939:Epitopes