title: Induction of apoptosis in NK cells by monocyte-derived reactive oxygen metabolites.
abstract: Human NK cells (with CD3-/56+ phenotype) acquired features characteristic of apoptosis after incubation with autologous monocytes, as revealed by apoptotic nuclear morphology, degradation of DNA into oligonucleosomal fragments, and reduced nuclear interchalation of propidium iodide. In contrast, T cells (CD3+/56-) remained non-apoptotic. The monocyte-induced apoptosis in NK cells was prevented by catalase, a scavenger of hydrogen peroxide; whereas superoxide dismutase (a scavenger of superoxide anion), hydroxyl radical scavengers such as mannitol and deferoxamine, or the hypochlorus acid scavenger taurine did not prevent apoptosis. Sodium azide, a myeloperoxidase inhibitor, substantially reduced the monocyte-induced apoptosis in NK cells. Exogenous hydrogen peroxide, at concentrations exceeding 1 microns, induced apoptosis in both NK and T cells. Apoptosis induced by hydrogen peroxide occurred independently of synthesis of protein or mRNA and was blocked by the endonuclease inhibitor aurin tricarboxylic acid. Furthermore, oxidatively induced apoptosis in NK cells was inhibited by herbimycin A, indicating that apoptosis was dependent on protein kinases. Two to five times more hydrogen peroxide was required to induce apoptosis in T cells compared with NK cells. Similarly, NK cells were considerably more susceptible to apoptosis induced by the topoisomerase II inhibitor etoposide or by gamma-irradiation than were T cells. We conclude that monocyte-derived reactive oxygen metabolites kill NK cells by apoptosis and that NK cells are unusually sensitive to oxidatively as well as non-oxidatively induced apoptosis.
authors.affiliation: Department of Virology, University of Göteborg, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Hansson
authors.forename: A
authors.initials: A
authors.lastname: Asea
authors.forename: U
authors.initials: U
authors.lastname: Ersson
authors.forename: S
authors.initials: S
authors.lastname: Hermodsson
authors.forename: K
authors.initials: K
authors.lastname: Hellstrand
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D004720:Endonucleases / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D046911:Macromolecular Substances; D009000:Monocytes / Q000737:chemistry* / Q000201:enzymology / Q000276:immunology; D009195:Peroxidase / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000502:physiology*; D016897:Respiratory Burst / Q000276:immunology
chemical_list: D046911:Macromolecular Substances; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D009195:Peroxidase; D011505:Protein-Tyrosine Kinases; D004720:Endonucleases