PRDM1 and infection: Using adoptive transfer of CTV-labeled Blimp1-YFP+ Smarta CD4+ T cells followed by LCMV infection, we distinguished Blimp1-YFPhi nascent TH1 and Blimp1-YFPlo nascent TFH cells, at the 5th division at 60 h post-infection (Fig. 8b).