To verify that the rescued memory Th17 cell response was responsible for the improved bacterial clearance under conditions of IFN-γ deficiency, Ifng−/− mice were infected as described in Figure 1B and intraperitoneally injected with IL-17 neutralizing antibody following PR8 infection, following which the numbers of CFUs in the lungs of the mice were determined. This evidence concerns the gene IFNG and infection.