Various studies have analyzed the impact of immune infiltration in malignant transformation of OPMDs: increased T-cells CD4+ and CD8+ infiltration has a protective effects, while increased levels of programmed cell death protein 1 (PD-1) and programmed cell death protein ligand (PDL-1), decreased T-cells CD3+ and increased T-cells helper 1 infiltration promote cancer progression [96,97,98]. Here, PDCD1 is linked to cancer.