title: Interleukin-6 regulates the cytotoxic effect of tumour necrosis factor on U937 cells.
abstract: In this study, we demonstrate that low but not high concentrations of interleukin-6 (IL-6) potentiate the cytotoxic effect of tumour necrosis factor-alpha (TNF-alpha) on U937 cells, in a dose-dependent manner. Killing of U937 cells by 100 U/ml of TNF-alpha, was maximally potentiated by 50 U/ml of IL-6. No potentiation of cell killing was observed when the concentration of IL-6 was increased to 4000 U/ml. At a concentration of 50 U/ml, IL-6 up-regulated TNF receptor expression but no change in TNF receptor number was observed when the concentration of IL-6 was increased to 4000 U/ml. Low concentrations of IL-6 can also induce sub-cytotoxic doses of TNF-alpha (0.1 and 0.33 U/ml) to kill U937 cells. Up-regulation of TNF receptors by IL-6 is dependent on de novo protein synthesis since receptor induction is abolished in the presence of cycloheximide. Taken together the data suggest that the potentiation of cell killing observed by a combination of these lymphokines is mediated in part by IL-6-induced changes in TNF receptor expression.
authors.affiliation: Signal Transduction Laboratory, National University of Singapore.
authors.forename: J A
authors.initials: JA
authors.lastname: Cairns
authors.forename: G R
authors.initials: GR
authors.lastname: Guy
authors.forename: Y H
authors.initials: YH
authors.lastname: Tan
mesh_terms: D002460:Cell Line; D003602:Cytotoxicity, Immunologic / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D015850:Interleukin-6 / Q000276:immunology*; D016403:Lymphoma, Large B-Cell, Diffuse / Q000276:immunology* / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000276:immunology; D018124:Receptors, Tumor Necrosis Factor; D014407:Tumor Cells, Cultured / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology* / Q000378:metabolism
chemical_list: D015850:Interleukin-6; D011956:Receptors, Cell Surface; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha