<p>This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</p> <p>Our understanding of biliary epithelial cells (BEC) in physiobiology and
            immunology has steadily expanded. BEC transports IgA as well as IgM into bile,
            synthesizes and secretes various chemokines, cytokines, and expresses adhesion
            molecules involved in cell interaction and signal transduction. These then suggest
            a myriad of potential roles for BEC in defense from invading microorganisms as well
            as the pathogenesis of diverse immunologically driven diseases such as primary
            biliary cirrhosis (PBC), graft-versus-host disease, and primary sclerosing cholangitis
            (PSC). Despite the progress, there still remain many areas of BEC biology that
            require further investigation. Most importantly, it remains to be clarified that the
            extent to which the immunologic activities observed in BEC represent a BEC
            response to tissue injury or whether BEC themselves are the active participants
            in the pathogenesis of various cholestatic immunological diseases, including PBC
            and PSC.</p>
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Clin Dev Immunol. 2004 Sep-Dec; 11(3-4):205-213