I. INTRODUCTION Primary sclerosing cholangitis (PSC) is a progressive cholestatic liver disease characterized by multifocal strictures of intrahepatic and extrahepatic bile ducts, which frequently leads to biliary cirrhosis and liver failure. The aetiology of PSC is unknown but is thought to be (auto)immune-mediated. Nevertheless, in a number of randomized controlled trials a clear benefit of treatment with various immunosuppressive agents, such as D-penicillamine, methotrexate, corticosteroids or nicotine, could not be demonstrated. Although treatment with ursodeoxycholic acid (UDCA) improves serum liver tests and is prescribed on a large scale for PSC patients, this therapeutic modality may have no beneficial effect on the course of the disease.