To study whether the decreased degranulation capacity of LCMV-specific CD8+ T cells in the livers of CIITA−/− mice was a consequence of T-cell exhaustion, we analyzed the expression of the major exhaustion marker PD-1 on LCMV-specific CD8+ T cells in the liver at day 15 after infection; PD-1 is considered to be the first exhaustion marker expressed by increasingly dysfunctional CD8+ T cells [30]. This evidence concerns the gene CD8A and infection.