We investigated the effect of human peripheral blood monocytes on the augmentation of natural killer cytotoxicity by α or γ natural and recombinant interf erons (IFN) and certain interferon inducers. We observed that: (1) in the majority of the donors examined (75) human peripheral blood monocytes do not affect natural killer cytotoxicity, determined by a 4-hour chromium-51 release assay, against target cells from hemopoietic human tumor cell lines. (2) Monocytes are not required and do not affect the augmentation of natural killer cytotoxicity by Escherichia coli-derived IFN-γ, natural human IFN-γ, E. Coli-derived IFN-α2 or natural human IFN-α. E. Coli-derived IFN-/and natural human IFN-γhave been reported to activate monocyte cytotoxicity determined in 72-hour assay. (3) Monocytes are not required for the augmentation of natural killer cytotoxicity against target cells from hemopoietic tumor cell lines by polyinosinic acid-polycytidylic acid or staphylococcal enterot
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