Interactions between endogenous gamma interferon and tumor necrosis factor in host resistance against primary and secondary Listeria monocytogenes infections.

Intravenous injection of rat anti-mouse gamma interferon (IFN-gamma) monoclonal antibody as well as rabbit anti-mouse tumor necrosis factor (TNF) antibody into mice which had received a sublethal infection with Listeria monocytogenes cells resulted in acceleration of listeriosis. Endogenous IFN-gamma seemed to be produced early in infection, because suppression of antilisterial resistance was significant when a single injection of anti-IFN-gamma monoclonal antibody was given on day 0 or day 1 of infection. Production of TNF but not of IFN-gamma in the bloodstream early in infection was inhibited by administration of anti-IFN-gamma monoclonal antibody. The suppressive effect of anti-IFN-gamma and anti-TNF antibodies on antilisterial resistance was not augmented by simultaneous administration of these antibodies. On the other hand, in the secondary infection, simultaneous administration of anti-IFN-gamma and anti-TNF antibodies, but not of either of these antibodies alone, into L. monocytogenes-immune mice resulted in high mortality and explosive multiplication of bacterial cells in the spleens and livers. These results suggest that endogenously produced IFN-gamma and TNF are both essential to the host defense against L. monocytogenes infection and that these cytokines might act by different modes between the primary infection and the secondary infection.