TCF7 and viral infectious disease: Transcription factor TCF1 is expressed at an extremely high level in Tfh cells post-viral infection and exerts crucial roles in generation, maintenance, and effector functions of Tfh cells by repressing Prdm1 and Il2ra and promoting Bcl6 expression (Shao et al., 2019; Wu et al., 2015; Choi et al., 2015; Xu et al., 2015).