Dipeptidyl peptidase IV (CD26) is a membrane-associated enzyme that is expressed on the surface of T cells and on the hepatocyte brush border. In a soluble form it is present in serum. CD26 has been implicated in the regulation of T cell activation and in the metabolism of hormones and cytokines. Dipeptidyl peptidase (DPP) activity is elevated in the urine and serum of patients with biliary atresia (BA). To clarify the role of cholestasis in the development of increased serum and urinary DPP/CD26 activity, we studied the mechanism of activity increase in experimentally induced cholestasis of CD26-deficient and wild-type rats. The clinical utility of serum and urinary DPP/CD26 activity measurements was tested in adult and pediatric patients with hepatobiliary diseases and in liver transplant recipients. The results establish CD26-associated serum DPP activity as a novel, clinically useful marker of cholestasis and demonstrate that in contrast with alkaline phosphatase levels, DPP levels do not change in metastatic bone disease. Additionally, DPP activity is useful as a urinary test of cholestasis in infants who are not receiving nephrotoxic medication.
ASJC Scopus subject areas
- Pathology and Forensic Medicine