The transcription factor TCF-1 initiates the differentiation of T FH cells during acute viral infection

Follicular helper T cells (TFH cells) require the transcription factor Bcl-6 and are antagonized by the transcription factor Blimp1 (encoded by Prdm1). Lilin Ye and colleagues show that acute viral infection induces the transcription factor TCF-1, which promotes TFH differentiation by enhancing Bcl6 expression while suppressing that of Prdm1.