Steroid Sensitivity of the Response of Human Lymphocytes to Phytohemagglutinin and Pokeweed Mitogen: Role of Phagocytic Cells

Populations of human peripheral blood lymphocytes were stimulated in vitro with phytohemagglutinin (PHA) or pokeweed mitogen (PWM) The presence of various concentrations of water‐soluble prednisolone inhibited this response in a dose‐dependent fashion Removal of phagocytic cells from the cell preparations increased steroid sensitivity of both the PHA and PWM responses a 100‐fold or more Medium obtained from cultures of unpurified populations of lymphoid cells, but not from purified populations, rendered purified lymphocytes more resistant to steroids both when PHA and PWM were used as stimulants A similar protective activity against steroids was observed in media conditioned by adherent cells obtained from peripheral blood. The results indicate that the monocyte‐macrophage cell line produces a factor that protects lymphocytes from the effects of corticotds.