title: Further evidence against a role for toxic oxygen products as lytic agents in NK cell-mediated cytotoxicity.
abstract: Natural killer (NK) cells are implicated in host defense mechanisms against infectious diseases and malignancies, and exert a rapid spontaneous cytolysis of various tumour cells and virus-infected cells without prior sensitization or activation (Herberman & Ortaldo, 1981). Human NK cells are a subpopulation of non-adherent, non-phagocytic lymphocytes defined as large granular lymphocytes (Timonen, Ortaldo & Herberman, 1981). NK cells possess a receptor for the Fc region of IgG (Perussia et al., 1984) that enables them to attack antibody-loaded targets, a process called antibody-dependent cell-mediated cytotoxicity (ADCC). The cytotoxic reaction of NK cells can be described as a 'stimulus-secretion' model, divided into three definable steps: binding, triggering for lysis and a killer cell-independent lytic step (Hiserodt, Britvan & Targan, 1982). The killing reaction involves a Ca2+-dependent activation, cytoskeletal rearrangement, activation of the arachidonic acid cascade, release of lysosomal enzymes and a cytotoxic factor(s) (Henkart, 1985) and, possibly, production of reactive oxygen species (Helfand, Werkmeister & Roder, 1982; Roder et al., 1982). The role and involvement of reactive oxygen species is still controversial. To study a possible participation of toxic oxygen species in NK-cell mediated cytotoxicity, we altered target cell anti-oxidant defence mechanisms and measured spontaneous NK-cell mediated cytotoxicity and ADCC reactions against tumour cells. We showed that alteration of target cell anti-oxidant systems had no effect on target cell susceptibility to NK-cell mediated killing. In contrast, the susceptibility of the anti-oxidant-depleted targets to oxygen-dependent polymorphonuclear leucocyte (PMN)-mediated cytotoxicity was increased.
mesh_terms: D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects; D000975:Antioxidants / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D004915:Leukemia, Erythroblastic, Acute / Q000276:immunology; D008223:Lymphoma / Q000276:immunology; D009504:Neutrophils / Q000276:immunology; D010100:Oxygen / Q000502:physiology*; D014407:Tumor Cells, Cultured / Q000276:immunology*
chemical_list: D000975:Antioxidants; D010100:Oxygen