Effects of tumour promoter phorbol myristate acetate on mouse lymphocytes: selective inhibition of B cell activation by mitogens and antigens.

The effect of the tumour promoter phorbol myristate acetate (PMA) on the responses of mouse lymphocytes to various stimuli was studied in vitro. Nanomolar concentrations of PMA inhibited B cell proliferation induced by lipopolysaccharide and by anti-Ig antibodies, and the polyclonal antibody response to lipopolysaccharide. Specific antibody responses to both T-dependent and T-independent antigens were similarly affected. In marked contrast, T cell proliferation elicited by various mitogens was 10- to 1000-fold more resistant to inhibition. Cell fractionation experiments suggest that the effects on B cell responses are the results of a direct anti-proliferative effect of PMA on responding B lymphocytes.