Induction of interferon-gamma production by human natural killer cells stimulated by hydrogen peroxide.

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Abstract
Interferon (IFN)-inducing activity of hydrogen peroxide in human peripheral mononuclear cells was investigated. Among the mononuclear cells, purified nonadherent cells produced IFN, but not B cells and monocytes. The maximal titer of IFN by purified nonadherent cells was observed after a 72-hr cultivation in the presence of 10(-2) mM H2O2 without affecting their viability. Furthermore, the purified nonadherent cells, but not the unpurified mononuclear cells, showed an augmented cytotoxicity to K562 when stimulated with hydrogen peroxide. By using Percoll discontinuous density gradient centrifugation, peripheral blood nonphagocytic and nonadherent mononuclear cells were divided into the low and high density fractions for which natural killer (NK) cells and T cells were enriched, respectively. The NK-enriched low density fractions, but not the T cell-enriched high density fractions, showed IFN production by the stimulation of hydrogen peroxide. IFN production as well as large granular lymphocytes and HNK-1+, Leu-11+ cells of the NK-enriched fractions were abrogated by treatment of the cells with monoclonal antibody against human NK cells (HNK-1+) but not against T cells (OKT3) in the presence of complement. Moreover, hydrogen peroxide-inducing IFN production seems to be regulated by monocytes. The antiserum neutralizing IFN-alpha and IFN-beta failed to neutralize substantially IFN-produced NK cells. The treatment with either pH 2 or antiserum-neutralizing human IFN-gamma resulted in marked reduction, indicating that a major part of IFN was IFN-gamma. The purified nonadherent cells showed IFN production and augmented cytotoxicity when cultured separately from activated macrophages by opsonized zymosan; furthermore, both IFN production and enhancement of cytotoxicity were abrogated by catalase. These results suggest that both exogenous and endogenous hydrogen peroxide might be responsible for a part of immunoregulation.