Enhancement of human monocyte cytotoxicity by both interferon-γ and -β and comparison to other stimuli

Recombinant interferon preparations caused a dose-dependent increase of human monocyte cytotoxicity to the K562 and Daudi cell lines. Both rIFN-γ and rIFN-β enhanced this function to a similar extent, while rIFN-α_c had less effect when compared on the basis of their anti-viral effects. Endotoxin and concanavalin A increased basal monocyte cytotoxicity while phagocytosis of latex particles had no effect. The increased monocyte cytotoxic effect of rIFN-β was completely abrogated by monoclonal antibody to IFN-β, while monoclonal antibody to IFN-γ had no effect. However, monoclonal antibody to IFN-γ only reduced the increased cytotoxic effect caused by rIFN-γ by 25%. Catalase inhibited both basal monocyte cytotoxicity and the increase in cytotoxicity following addition of rIFN-γ only slightly, suggesting that mechanisms other than the oxidative burst were active and could be induced by rIFN-γ.