Type I interferons enhance production of IFN-γ by NK cells

In murine models, challenge with different viral and parasitic infection is closely associated with the production of type I interferons (IFN-alpha/beta) and NK cell production of interferon-gamma (IFN-gamma). Therefore, we wished to determine if IFN-alpha/beta had a role in the regulation of NK cell production of IFN-gamma. IFN-alpha/beta alone stimulated low levels of IFN-gamma production by purified populations of IL-2 activated NK cells but in combination with IL-12 resulted in the production of significant levels of IFN-gamma. Interestingly, maximal production of IFN-gamma by NK cells stimulated with IL-2 plus IFN-alpha/beta was dependent on endogenous tumor necrosis factor-alpha (TNF-alpha). Further studies revealed that TNF-alpha enhanced the ability of IFN-alpha/beta to stimulate production of IFN-gamma by NK cells. In contrast to the stimulatory effect of IFN-alpha/beta on NK cell production of IFN-gamma, IFN-alpha/beta inhibited IL-2 induced proliferation of NK cells. This inhibitory effect was not reversed by the addition of neutralizing antibodies specific for IFN-gamma or TNF-alpha. These data demonstrate that the type I interferons enhance NK cell production of IFN-gamma and suggest that they may be important in the regulation of NK cell production of IFN-gamma during infection.