Abstract

Aim: Sera of patients with autoimmune liver diseases were investigated for the presence of autoantibodies binding to human biliary epithelial cells (BECs). Furthermore, their functional capacity was investigated by testing their capacity to fix complement as well as induce expression of various adhesion molecules and production of cytokines.

Methods: Sera from patients with various stages of primary sclerosing cholangitis (PSC; n=30), primary biliary cirrhosis (PBC; n=29), autoimmune hepatitis (AIH; n=25), and normal controls (n=12) were investigated for the presence of antibodies that reacted with unstimulated and cytokine stimulated BECs isolated from a normal healthy liver. To demonstrate organ specificity, lung epithelial cells (LECs) were used as control cells. Antibodies were tested for their functional capacity.

Results: Compared with controls (8%), significantly higher numbers of PSC patients (63%, p=0.001), but not PBC (37%, NS) or AIH (16%, NS) patients, had anti-BEC antibodies. In 90% of PSC patients, the autoantibodies reacted only with cytokine stimulated target cells. Lower numbers of PSC (6%), PBC (10%), and AIH (0%) patients had LEC antibodies. Other significant findings were that anti-BEC antibodies were found in (i) PSC patients with either the HLA-DRB1*0301 or DR2 allele compared with those without (p=0.007); and (ii) in PBC patients with end stage disease compared with those without (p=0.018). Furthermore, anti-BEC antibodies from PSC and PBC but not AIH patients induced BECs to produce high levels of the cytokine interleukin 6. IgM and IgG fractions isolated from PSC but not PBC and AIH sera induced significantly increased expression of the cell adhesion molecule CD44. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis and western blot analysis of BEC membranes demonstrated a specific band of 40 kDa with PSC sera and 45, 42, 30, and 33 kDa bands with PBC sera, which were absent in control groups.

Conclusion: Thus for the first time we have demonstrated the presence of functionally important autoantibodies to cell surface expressed antigens on the relevant target cells of destruction, namely BECs, in PSC and PBC. These finding have important implications for the pathogenesis of bile duct destruction in these patients.