In order to investigate the effector potential of the MCMVspecific 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-c 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 ). For each of these parameters, we observed an accelerated acquisition of effector functions by CD8 T cells from Klra8 mice when compared to BALB/c animals.