title: In vitro effects of leukocyte interferon on the cytotoxic potential of human monocytes.
abstract: The in vitro cytotoxicity of human monocytes was enhanced by leukocyte interferon (IFN-alpha). In contrast to lymphokine activation which is obtained gradually under long-term contact with monocytes, maximal activation of effector cells was obtained within 4 hours of culture with IFN-alpha prior to medium exchange and target cell addition. The degree of activation was clearly dose-dependent, reaching a plateau level of cytolysis at 400 U/ml of IFN-alpha. In cytostasis no such plateau was demonstrable. IFN-alpha enhanced the level of cytolysis mediated by human monocytes without inducing any change in the kinetics of lysis, regardless of whether IFN-alpha was used for activation of monocytes prior to or simultaneously with the cytolysis assay. The direct effect of IFN-alpha on K-562 target cells was sparse. The incorporation of thymidine was modestly depressed in the presence of IFN-alpha. Exposure of K-562 cells to IFN-alpha did not have any effect on the spontaneous isotope leakage from prelabelled target cells. The exposure of K-562 cells to IFN-alpha prior to the start of co-culture with monocytes did not change the level of cytolysis reached, either with non-activated or with IFN-alpha activated monocytes, and irrespective of the in vitro age of the monocytes. The effect of IFN-alpha thus seems to be mediated via the effector cell population and not via target cell modulation.
mesh_terms: D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003601:Cytotoxicity Tests, Immunologic / Q000379:methods; D003602:Cytotoxicity, Immunologic; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D007370:Interferon Type I / Q000494:pharmacology / Q000502:physiology*; D007700:Kinetics; D008222:Lymphokines / Q000502:physiology; D009000:Monocytes / Q000276:immunology* / Q000502:physiology; D013997:Time Factors
chemical_list: D007370:Interferon Type I; D008222:Lymphokines