C57BL/6 Perforin−/− mice that lack the cytotoxic potential show a higher susceptibility and lethality upon infection with R. australis compared to C57BL/6 IFNγ−/− mice, although being much less susceptible than C57BL/6 MHCI−/− that lack CD8+ T cells at all [46]. This evidence concerns the gene IFNG and infection.