CD8A and viral infectious disease: To further confirm the intrinsic regulation of TCF1 on CD8 T cells during chronic viral infection, we generated bone marrow chimera mice by reconstituting irradiated WT recipient mice (CD45.1) with a mixture of congenitally marked bone marrow cells from Tcf7fl/fl-CD4Cre donor mice (CD45.2, 30%) and WT donor mice (CD45.1, 70%) (Figure 3A).