PDCD1 and neoplasm: The presence of NK cells prevented formation of a more exhausted status of tumor-infiltrating CD8+ T cells even under conditions of PD-L1 blockade, as evidenced by decreased expression of degranulation marker CD107a, and effector cytokines, TNF-α and IFN-γ, and increased expression of exhaustion marker PD-1 by CD8+ T cells, after NK cell depletion (28).