IL17A and demyelinating disease: Because virus-reactive IFN-γ-producing Th1 cells are protective, but IL-17-producing Th17 cells are known to inhibit Th1 development and cytotoxic T cell functions [13,54], FoxP3+CD4+ T cells, together with Th17 cells, may promote the pathogenesis of TMEV-induced demyelinating disease.