CD8A and viral infectious disease: As expected, different subsets of memory CD8+ T cells from three viral infections differed greatly in proportion (Figures 1B, C) and three effector T-cell subsets (cluster0,2,6, Tem), four terminally differentiated effector T-cell subsets (cluster1,5,7,8, Temra), one central memory T-cell subset (cluster3, Tcm), and one stem-like central memory T-cell subset (cluster4, Tscm) were defined according to expression of marker genes that were defined by previous studies (18–21) (Figure 1D).