Effects of phorbol myristate acetate on interleukin-2 and accompanying interferon production of human leukocytes induced by heat-inactivated Staphylococcus aureus.

Interleukin-2 (IL-2) production induced by heat--inactivated Staphylococcus aureus (SAU) was enhanced by simultaneous addition of phorbol myristate acetate (PMA). The effect was optimal at a concentration of 10 ng/ml SAU; in the presence of 10 ng/ml PMA, the amount of SAU required for maximal IL-2 production was lower. The kinetics of SAU and of SAU plus PMA-induced IL-2 production were similar. Stimulated mononuclear cells produced interferon (IFN) in addition to IL-2. The titre of accompanying IFN was decreased in cultures stimulated with the SAU plus PMA combination. Plastic nonadherent sheep erythrocyte-positive cells were the most active in the SAU-induced IL-2 production. In contrast, the bulk of the IFN activity was produced by the nonadherent E rosette-nonforming cells. Neutralization of IFN with specific antibodies and pH 2 treatment indicated that SAU-induced IFN consisted mainly of alpha-IFN.