CD4 and infection: Similar to the impaired TFH differentiation of GP66–77 tetramer-positive CD4+ T cells in Ezh2fl/flCd4-Cre mice upon infection, the bulk-activated Foxp3−CD44hiCD4+ T cells from these mice also exhibited compromised CD44hiCXCR5+TFH differentiation, as evidenced by the decreases in the proportion of TFH cells, the TFH to TH1 ratio and the absolute TFH number compared to that in Ezh2fl/fl control mice (Supplementary Figure S4b–d).