Induction of interferon production by natural killer cells by organogermanium compound, Ge132

Interferon (IFN)-inducing activity of the organogermanium compound Ge132 in human peripheral mononuclear cells was investigated. By using Percoll discontinuous density gradient centrifugation, peripheral blood nonphagocytic and nonadherent mononuclear cells were divided into the low-and high-density fractions. Natural killer (NK)-enriched low-density fractions, but not the T-cell-enriched high-density fractions, showed IFN production by the stimulation of Ge132. The maximal titer of IFN by NK-enriched fractions (F1 + F2) was observed after a 74-h cultivation in the presence of 200 micrograms/ml Ge132. IFN production by the NK-enriched fractions was abrogated by treatment of the cells with monoclonal antibody against human NK cells in the presence of complement. The treatment with antiserum-neutralizing human IFN-gamma resulted in a marked reduction, indicating that a major part of IFN was IFN-gamma. These results suggested that Ge132 might possess affinity to NK cells, inducing IFN production by NK cells.