At 8 days post-infection (dpi), the frequency of splenic CD8+ T cells that produced IFN-γ in ex vivo stimulations with ΔMHCIi-infected DC2.4 cells was significantly reduced in WT CPXV- and ΔMHCIi-infected Batf3-/- mice (Fig 2A) in comparison to infected B6 mice, confirming the importance of cross-presentation (or cross-dressing) in inducing CPXV-specific CTLs, as we showed earlier [5]. This evidence concerns the gene IFNG and infection.