In vitro synergistic effects of interferon on human lymphotoxin activity: a new property of interferon in lymphocyte-mediated target cell killing.

Our recent studies have demonstrated a significant enhancement of human lymphotoxin (LT) induced in vitro target cell killing by human alpha and beta interferons (IFN), including highly purified recombinant DNA-produced IFN. This synergistic effect of IFN on LT activity was dose dependent, observed with as little as 10 U/ml IFN, was demonstrable on human normal and tumor cells, and was blocked by treatment with antiserum to IFN. When IFNs and target cells from other animal species were tested, a new finding was made showing protective effects of IFN on human LT activity. IFN-induced enhancement or protection depended on the particular IFN:target cell combination, with the highest degree of enhancement being observed in the homologous human combination. These results describe a new property of IFN in lymphocyte-mediated target cell killing and are discussed in relationship to previously observed enhancing and protective effects of IFN in natural killer (NK) cell systems, as well as to the role of IFN in viral infection.