Microarray successfully displayed characteristic differential cDNA expression between small and large cholangiocytes. This technique provides molecular information, which further supports our hypothesis that small and large bile ducts have different functions.

Bile-duct injury 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-mediated cell death in this immune-mediated cholangiopathy. In this study, we first showed the constitutive expression of Fas receptor by cholangiocytes in situ from normal BALB/c mice, which was upregulated in GVHD mice. Also, we confirmed the Fas protein expression in the isolated cholangiocytes from normal BALB/c mice by immunocytochemistry and immunoblotting. Furthermore, the addition of Bile-duct injury or cholangiopathy is observed in hepatic graft versus host disease (GVHD). 1 Nondestructive or destructive cholangitis with degeneration of bile-duct epithelium, as seen in primary biliary cirrhosis (PBC), is a hallmark of acute GVHD. 2 These immune-mediated cholangiopathies eventually develop hepatic failure. Indeed, chronic allograft rejection, another form of immune-mediated cholangitis, is one of the leading causes of hepatic allograft loss. However, the precise mechanism of cholangiocyte injury is unknown. Subsequently, animal models of GVHD have been developed to study the mechanism of cholangiopathies. Those murine models of GVHD showed the minor histocompatibility antigen is believed to be the main target, and the nature of inflammation, mainly CD4-positive or CD8-positive lymphocytes, were well documented. 3 However, the cellular mechanism of cholangiopathy occurring in GVHD is still unclear. Recently, apoptosis is found to be involved in several inflammatory processes. 4,5 The Fas, a 45-kd type I cell-surface receptor, is a member of tumor necrosis factor (TNF) receptor superfamily. 6 Stimulation of Fas receptor with its ligand, FasL, leads to apoptosis. 7,8 In mice, the administration of agonistic Fas antibody leads to fulminant hepatic failure in the recipients. 9 In liver diseases related to hepatitis virus infection, Fas is identified on hepatocytes, suggesting that cell death of hepatocytes occurs through Fas/FasL interaction. 10 Fas antigen expressions by cholangiocytes were reported previously in humans 11 and rats, 12 and enhanced expression of Fas antigen on cholangiocytes was also reported in PBC. 13 However, the states of Fas expression in normal cholangiocytes in mice and the role of Fas/FasL system in immune-mediated cholangiopathies remain unknown. In this study, we investigated the Fas receptor expression by cholangiocytes and its role in cholangiopathy in murine GVHD model. Furthermore, we show the efficacy of the blocking of Fas/FasL system using both in vitro and in vivo, which might give novel therapeutic strategies to progressive human hepatobiliary diseases. MATERIALS AND METHODS AnimalsBALB/c CrSlc mice (H-2 d , MLS 3a ), B10.D2 nSn mice (H-2 d , MLS 3b ), and MRL/Mp J (lpr/lpr) mice, all of which were female and 6 weeks of age, were purchased from Japan SLC (Hamamatsu, Japan) and fed ad libitium under a standard animal-care manual

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Disequilibrium mapping using microsatellite markers was a useful method to narrow a disease susceptibility locus. The possible susceptibility gene in the HLA region is thought to be localized around or in the TNF gene. Further studies seem feasible using more closely distributed microsatellite markers or single nucleotide polymorphisms (SNPs) to narrow the susceptibility locus in PBC in Japanese populations.