In certain other conditions including autoimmune diseases, lung adenocarcinoma, hepatocellular carcinoma, B-chronic lymphoblastic leukemia, and T acute lymphoblastic leukemia, enhanced expression of CD26 is detectable, but previous reports claimed that inhibition of CD26 does not suppress the activation and cytotoxic effect of T cells [68,69,72]. Here, DPP4 is linked to autoimmune disease.