MKI67 and infection: In order to investigate the effector potential of the MCMV-specific CD8 T cells observed at day 4 post-infection in Klra8 mice, we measured different parameters associated with the protective functions of antiviral CD8 T cells, namely their proliferation, by monitoring the expression of the marker Ki-67 (Figure 4A), their capacity to produce IFN-γ in response to antigen-specific restimulation in vitro using intracellular staining (Figure 4B) and ELISPOT (Figure S3), and their cytotoxic potential by measuring antigen-specific target cell killing in vivo (Figure 4C).