CD8A and cancer: On the other hand, blocking the inducible costimulator (ICOS or CD278)–ICOS-ligand (ICOSL) interaction supports the generation of effector-like PD-1+CD8+T cells, reduces the viral load, and improves the response to PD-1 blockade in CVIs and cancer TME due to overexpression and overactivity of FoxO1, as it serves as a master regulator of memory programming in human CAR T cells [190,191].