CD8A and neoplasm: Such analyses have revealed that the “dysfunctional” CD8+ T cells have undergone the highest level of clonal expansion among the various tumor infiltrating T cell subpopulations (Figure 1; Zheng et al., 2017; Azizi et al., 2018; Guo et al., 2018; Sade-Feldman et al., 2018; Zhang et al., 2018; Li H. et al., 2019; Yost et al., 2019).