As the absolute numbers of CD4+ T cells in the brains of IL-17R KO and WT mice were similar at day 7 post-infection, the increased IL-17 levels observed in KO mice are likely to be attributed to either cytokine accumulation based on receptor absence or, alternatively, the significantly larger population of γδ T cells infiltrating the CNS of IL-17R KO mice that can also produce IL-17. This evidence concerns the gene CD4 and infection.