Given the changes in gene expression affecting cell proliferation, TCR and cytokine-mediated proliferation of GFI1ΔCD8 CD8+ TM cells, isolated from spleen of LCMVc13-infected mice at day 7 after infection, was quantitated by culturing CD8+ TM cells in vitro with IL-2 + IL-7 or IL-2 + CD3/CD28 stimulation beads (Extended Data Fig. 9a). This evidence concerns the gene CD28 and infection.