IFNG and infection: After infection with the Ts strain, the expression levels of IFN-γ and IL-12p40 genes in the bursa were not significantly different at 1 and 3 dpi (P > 0.05 for both genes at both time points), but then increased significantly at 5 dpi (P = 0.006 for IFN-γ and 0.02 for IL-12p40) (Figure 2B and 2F).