TCF1 is required for the differentiation of T follicular helper (TFH) cells during viral infections. Mus musculus

TFH and Th1 cells generated after viral or intracellular bacterial infections are critical for the control of infections and the development of immunological memories. However, the mechanisms that govern the choice of activated CD4 T cells to the two alternative fates remain unclear. Here, we found that reciprocal expression of TCF1 and Blimp1 between viral-specific TFH and Th1 cells started early after infection. TCF1 was intrinsically required for the differentiation of TFH cells. In the absence of TCF1, TFH cells failed to maintain their transcriptional and metabolic signatures, distinct from those in Th1 cells. Mechanistically, TCF1 functioned through forming negative feedback loops with IL-2 and Blimp1 signaling. Thus, we have demonstrated an essential role of TCF1 in TFH-cell differentiation. Overall design: Tcf7 deficient and WT SMARTA CD4 T cells were isolated from mice 8 days after Lymphocytic Choriomeningitis Virus (LCMV) infection. TFH and Th1 cells were separated by FACS.