Pathogenesis of immune-mediated cholangiopathy

肝移植物抗宿主病（GVHD）中的胆管损伤被认为是一种免疫介导的损伤，尽管其确切机制尚不清楚。然而，最近的研究表明，Fas介导的细胞死亡参与这种免疫介导的胆管病。在本研究中，我们首次证实了正常BALB/c小鼠原位胆管细胞Fas受体的组成性表达，在GVHD小鼠中上调。此外，我们还通过免疫细胞化学和免疫印迹证实了Fas蛋白在正常BALB/c小鼠胆管细胞中的表达。此外，通过DNA梯状条带形成和膜联蛋白V染色证实，加入激动性Fas抗体（Jo 2）诱导胆管细胞凋亡。Fas缺陷小鼠（MRL lpr/lpr）的胆管细胞未显示出Jo 2诱导的凋亡。γ干扰素分别增强Fas表达和Fas介导的细胞死亡。在这些观察之后，通过将来自B10.D2小鼠的脾细胞转移到经照射（800 rad）的BALB/c小鼠来诱导实验性GVHD。受体肝脏浸润淋巴细胞对<51>BALB/c小鼠分离的~ 13 Cr标记的胆管细胞显示出剂量依赖性细胞毒性。此外，添加阻断性Fas-Fc融合蛋白将这种细胞毒性降低至44.7%。最后，将该Fas-Fc蛋白给予已经过继转移了B10.D2小鼠脾细胞的BALB/c小鼠，防止了体内肝GVHD的发展。这些结果表明Fas介导的细胞死亡参与GVHD中观察到的胆管病变，可溶性Fas-Fc蛋白可能具有治疗肝脏GVHD的潜力。

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 demonstrated 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 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 γ augmented Fas expression and Fas-mediated cell death, respectively. Following these observations, experimental GVHD was induced by transfer of splenocytes from B10.D2 mice to irradiated (800 rad) BALB/c mice. Liver infiltrating lymphocytes from the recipient showed dose-dependent cytotoxicity against ^<51>Cr-labeled cholangiocytes isolated from BALB/c mice. Moreover, the addition of blocking Fas-Fc fusion protein reduced this cytotoxicity to 44.7%. Finally, administration of this Fas-Fc protein to the BALB/c mice, which had been adoptively transferred with splenocytes of B10.D2 mice, prevented the development of hepatic GVHD in vivo. These results demonstrated the involvement of Fas-mediated cell death in cholangiopathy observed in GVHD, and a soluble Fas-Fc protein may have a therapeutic potential for hepatic GVHD.