CD8A and infection: To determine whether GFI1hi and GFI1lo CD8+ T cells differed in their capacity to respond to a secondary infection, GFI1hi and GFI1lo CD8+ T cells were isolated from the spleen of LCMVArm-infected wild-type (WT) mice on day 21 after infection and adoptively transferred into secondary recipients that were challenged with LCMVArm the next day (Extended Data Fig. 3c).