To illustrate the expression of the inhibitory checkpoint receptor PD-1 on CD8+ T lymphocytes, or its cognate ligand PD-L1 on tumor or immune cells, attenuates T cell effector functions, blocking this PD-1/PD-L1 interaction and consequently it mitigates T cell exhaustion and augments the host's immunological efficacy against malignant cells [23–25]. Here, PDCD1 is linked to neoplasm.