The expression of MAdCAM-1 by portal and not sinusoidal endothelium, as well as presence of other chemokines and integrins like CCL28 and β7 in and around the bile ducts suggest that the inflammatory trigger in PSC originates in the portal area, i.e. in the bile ducts, thereby provoking cholangitis and not hepatitis. This evidence concerns the gene MADCAM1 and cholangitis.