PRDM1 and viral infectious disease: Several recent studies revealed that the transcription factor TCF-1 is expressed at high levels in Tfh cells after viral infection and plays an essential role in their generation and maintenance, via repression of Il2ra, and Prdm1 (which encodes BLIMP1), promotion of Bcl6 (55, 88–90), and possibly repression of Ifng (91).