Dipeptidyl peptidase IV (DPP IV) is widely distributed in a number of mammalian tissues and is suggested to play an important role in various kinds of biological processes. DPP IV (CD26) is a serine-type protease that removes the amino-terminal dipeptide from peptide substrate provided that the penultimate amino acid residue is proline or alanine. DPP IV plays an important role in the reclamation of peptide nitrogen from larger peptides.The monoclonal antibody 5E8 reacts with DPP IV present on the apical surface of epithelial cells in the pancreas, small intestine, colon, and bile duct. Furthermore antibody 5E8 reacts with DPP IV on the laminar portions of the proximal renal tubule cells, and, weakly, on the glomeruli.