Medullasin enhances human natural killer cell activity by a mechanism other than the induction of interferons or interleukin-2.

The mechanism of activation of human natural killer cell activity by medullasin was studied with special reference to interferons and interleukin-2. Supernatant of lymphocytes treated with medullasin failed to stimulate natural killer cell activity when added to the lymphocyte suspension. Medullasin has been shown to enhance the natural cytotoxicity of lymphocytes stimulated with interferon-alpha or -beta. In the present study, medullasin increased the natural killer cell activity of lymphocytes stimulated with interferon-gamma. Treatment of lymphocytes with medullasin in the presence of antibodies to interferons (alpha, beta and gamma) did not alter the effect of medullasin. Medullasin also increased the natural cytotoxicity of lymphocytes stimulated with interleukin-2. The antibody to interleukin-2 failed to affect the increase of natural killer cell activity by medullasin. These results indicate that the mechanism of activation of human natural killer cell activity by medullasin is not mediated by the induction of interferons or interleukin-2.