Although expression of MHC-II mRNA can be detected by RT-PCR on activated CD8 T cells following acute LCMV infection (Fig. S4a), no substantial presence of MHC-II was detected by flow cytometry at 36 hours post-infection when CD8 T cells were activated in MHC-II knockout mice (CIIKO, Fig. S4b). Here, CD8A is linked to infection.