Lack of inhibition of mitogen-induced lymphoproliferation by interferon gamma

Interferon (IFN) gamma has been shown to have enhancing effects on immunocompetent cells, as for example induction of the expression of I-A antigens. In this report the effect of purified mouse IFN-gamma on mitogen-induced proliferation was studied. In contrast to the situation observed with IFN-alpha or IFN-beta, treatment by IFN-gamma had no suppressive effect on mitogenesis. Enhancing effects on DNA synthesis induced by phytohemagglutinin were observed at low concentrations of IFN-gamma in the early stage of lymphocyte activation. The effects on T cell proliferation, however, were not consistent under all experimental conditions.