Within the first 4–5 days of acute LCMV Armstrong infection, activated CD8+ T cells uniformly acquire effector characteristics, including cytotoxic capacity and IFNγ production, but can be phenotypically partitioned into KLRG1neg CD127+ memory precursor effector cells (MPEC) and KLRG1HI CD127neg/LO short-lived effector cells (SLEC) [27,28,29]. This evidence concerns the gene CD8A and infection.