PDCD1 and neoplasm: The binding of this substance to the inhibitor programmed cell death protein 1 (PD-1) or the binding of PD-1 to the immune co-inhibitory receptor lymphocyte activation gene-3 (LAG3) transmits an inhibitory signal, causing a reduction in the proliferation of antigen-specific T cells, and consequently a reduction in the infiltration of T cells into the tumour lesion [93,94,95].