IFNG and infection: Additionally, an intriguing observation of two γδ T cell subsets (Vγ1+ T cells and Vγ4+ T cells) was made in WNV-infected mice of different ages: By day 3 post-infection, Vγ1+ T cells in splenic cells of young mice rapidly expanded and represented the major subset of γδ T cells producing IFN-γ, while Vγ4+ T cell expansion was less pronounced.