ICIs function by alleviating inhibitory barriers on T cells, such as programmed cell death 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4), or by mitigating coinhibitory signals on tumor cells and antigen-presenting cells, like programmed cell death ligand-1 (PD-L1). Here, PDCD1 is linked to neoplasm.