IFNG and infection: Treatment of IL-12p40−/− with IL-18 bp also resulted in marked enhancement of viremia already at day 5 after infection (Figure 4C), results which are similar to those obtained in IFN-γ−/− mice (Figure 1I) and substantially different from results observed at day 5 in IL-12p40−/− mice or mice treated with IL-18 bp alone (Figure 4C).