Previous research demonstrated that Tcf1 plays an early role in Tfh differentiation during viral infection by directly promoting Bcl6 expression (Choi et al., 2015, Xu et al., 2015, Wu et al., 2015, Shao et al., 2019), suggesting that Dnmt3a indirectly silences Bcl6 expression in Th1 cells. Here, BCL6 is linked to viral infectious disease.