Fas-Mediated Cholangiopathy in a Murine Model of Graft-versus-Host Disease
Bile-duct injury, or cholangiopathy, observed in hepatic graft versus host disease (GVHD) is regarded as an immune-mediated injury, although its precise mechanism is unclear. However, recent studies have suggested the involvement of Fas (CD95) -mediated cell death in this immune-mediated cholangiopathy. We first demonstrated the constitutive expression of Fas receptor by cholangiocytes in situ from normal mice, which was upregulated during GVHD reactions. Also, we confirmed the Fas protein expression in the isolated cholangiocytes from normal BALB/c mice by both immunocytochemistry and immunoblotting. Furthermore, the addition of hamster agonistic Fas antibody (Jo2) induced cholangiocyte apoptosis confirmed by DNA-ladder formation and annexin V staining. Cholangiocytes from Fas-deficient mice (MRL lpr/lpr) did not show Jo2-induced apoptosis. Interferon-gamma augmented Fas expression and Fas-mediated cell death, respectively. Liver-infiltrating lymphocytes from the GVHD mice showed dose-dependent cytotoxicity against isolated cholangiocytes. Moreover, the addition of blocking Fas-Fc fusion protein reduced this cytotoxicity. Finally, administration of this Fas-Fc protein to the BALB/c mice in vivo prevented the development of hepatic GVHD. These results showed the involvement of Fas-mediated cell death in the cholangiopathy observed in GVHD.