title: Role of serotonin in the regulation of human natural killer cell cytotoxicity.
abstract: Addition of serotonin to mixtures of target cells and natural killer (NK)-enriched human mononuclear cells (MNC) in a 4-hr 51Cr-release assay strongly augmented NK cell cytotoxicity (NKCC) vs K562, Chang, or Molt-4 target cells. The effect was dose dependent at serotonin concentrations of 10(-4) to 10(-7) M, expressed at several effector to target cell ratios, and required the presence of accessory monocytes. A 5-HT1-specific receptor agonist, 8-OH-DPAT, mimicked the enhancing properties of serotonin with similar potency. Equimolar concentrations of the mixed 5-HT1/5-HT2 receptor antagonist cyproheptadine, but not the 5-HT2-specific antagonist ketanserin, completely blocked the serotonin-induced NKCC enhancement. Monocyte/NK cell mixtures incubated with serotonin for 1 hr produced a soluble factor that could enhance the cytotoxicity of autologous, NK-enriched cells depleted of monocytes, which did not respond to serotonin alone. The factor displayed no IFN or IL 2 activity as judged by the lack of antiviral activity and inability to support the growth of an IL 2-dependent cell line. In the presence of monocytes, serotonin (10(-5) M) was considerably more effective than human IFN-alpha or IFN-gamma at optimal concentrations and was about equally effective as IL 2 at a final concentration of 50 U/ml in a short-term NK assay. The potency and efficacy for serotonin were similar to that earlier reported for histamine in monocyte-containing effector cells. The NKCC-enhancing effect of serotonin was additive to that induced by IFN-alpha, IFN-gamma, or IL 2, but not to histamine. The presented data suggest an earlier unrecognized, serotonin receptor-mediated regulation of human NK cells.
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D003533:Cyproheptadine / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D004357:Drug Synergism; D006801:Humans; D007372:Interferons / Q000494:pharmacology; D007650:Ketanserin / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology*; D007959:Lymphocyte Culture Test, Mixed; D008222:Lymphokines / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology / Q000502:physiology*; D013268:Stimulation, Chemical; D013764:Tetrahydronaphthalenes / Q000494:pharmacology
chemical_list: D008222:Lymphokines; D011985:Receptors, Serotonin; D013764:Tetrahydronaphthalenes; D003533:Cyproheptadine; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D007372:Interferons; D007650:Ketanserin