TCF7 and infection: In the Tcf7fl/fl-CD4Cre bone marrow chimeras at 25 days after infection with LCMV Cl13 stain, we further confirmed the significantly reduced expression of Bcl6 and Eomes which have been confirmed to be crucial factors that regulate CD8 T cell functions (13, 26, 30–32) in exhausted Tcf7−/− CD8 T cells via flow cytometry analysis (Figure 5B, Supplementary Figure 4B).