IFNG and colitis: Notably, while the numbers and frequency of activated CD4+ T cells (CD62L−CD44+) were increased in colons of SPF + P mice during DSS colitis (Fig. 4d, e), the numbers of different CD4+ T helper (Th) subsets including Th1 (CD4+IFN-γ+) and Th17 (CD4+IL-17A+) cells as well as in regulatory T cells (CD4+Foxp3+) were not affected (Supplementary Fig. 4c).