A key advantage in the discovering T‐cell exhaustion using the LCMV mouse infection model was the different viral laboratory strains and/or different viral inoculum that induce either an acute infection that could be resolved or a persistent chronic infection.47, 48, 49 Although CD8 T‐cell dysfunction was known to be an essential feature of exhaustion, the identification of PD‐1 as a key player during chronic infection was revealed much later through gene expression analysis. Here, PDCD1 is linked to infection.