title: Cytolysis of tumor necrosis factor (TNF)-resistant tumor targets. Differential cytotoxicity of monocytes activated by the interferons, IL-2, and TNF.
abstract: Herein we demonstrate that IFN-alpha, IFN-gamma, and IL-2 can induce human peripheral blood monocyte-mediated lysis of tumor cells that are resistant to both the direct effects of TNF and to monocytes activated by TNF. Monocytes activated by TNF kill only TNF-sensitive tumor targets, whereas those activated by IFN and IL-2 can lyse both TNF-sensitive and TNF-resistant tumor targets. Monocyte cytotoxicity against TNF-sensitive lines induced by the IFN, IL-2, or TNF can be completely abrogated by the addition of anti-TNF antibodies. In contrast, anti-TNF antibodies have no effect on IFN- or IL-2-induced monocyte cytotoxicity against TNF resistant targets, confirming non-TNF-mediated lysis induced by lymphokine-activated monocytes. Neither induction of TNF receptors by IFN-gamma nor inhibition of RNA synthesis by actinomycin D increased the susceptibility of TNF-resistant tumor targets to TNF-mediated monocyte cytotoxicity. Thus, non-TNF-mediated modes of monocyte cytotoxicity are induced by IFN and IL-2, but not by TNF, indicating that different cytotoxic mechanisms are responsible for the lysis of TNF-sensitive and TNF-resistant tumor cells. In addition, these findings also suggest that TNF-sensitive lines are susceptible only to TNF-mediated killing and apparently insensitive to non-TNF-mediated monocyte cytotoxicity.
mesh_terms: D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D006801:Humans; D007372:Interferons / Q000494:pharmacology*; D007376:Interleukin-2 / Q000494:pharmacology*; D007963:Leukocytes, Mononuclear / Q000187:drug effects* / Q000276:immunology; D011994:Recombinant Proteins / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D007376:Interleukin-2; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007372:Interferons