DPP4 and autoimmune disease: Nonetheless, although many experimental and clinical findings indicate that DPP-4 plays a role in the pathogenesis of autoimmune diseases, DPP-4 inhibition has controversial effects in autoimmune or inflammatory diseases, which might be related to the ubiquitous tissue distribution and tissue-specific regulation of DPP-4/CD26, as well as to the numerous functions and effects of DPP-4/CD26 [46].