表現無唾液酸神經節苷脂之肝臟駐留記憶性T細胞 在原發性膽汁性膽道炎發病中的致病機制

Abstract

原發性膽汁性膽道炎是一種病程緩慢的自體免疫性肝炎，在病人可以檢測到血清中獨特的抗粒線體抗體、膽管受損以及肝纖維化等病徵。過去的研究顯示，T 細胞在原發性膽汁性膽道炎的發病機制中扮演著重要的角色，同時近期研究發現了一群具有組織駐留的記憶T細胞，對於非淋巴組織對抗病原體非常重要。我們實驗室過去發現利用無唾液酸神經節苷脂的抗體預處理可以抑制刀豆蛋白A誘導的急性肝炎與2-辛酸誘導的原發性膽汁性膽道炎。並且表現無唾液酸神經節苷脂之肝臟駐留CD8 T細胞在刀豆蛋白A誘導的急性肝炎早期活化並分泌促炎細胞素「干擾素γ」。然而，無唾液酸神經節苷脂之肝臟駐留CD8 T細胞如何影響原發性膽汁性膽道炎的早期疾病進展與致病機轉仍不清楚。本研究的結果證實，無唾液酸神經節苷脂的抗體預處理降低了小鼠血清抗粒線體抗體與干擾素γ的產生，降低干擾素γ與纖維化相關基因膠原蛋白(Collagen) I型、III型表現量，以及膽道周圍免疫細胞浸潤與纖維化的現象，顯示無唾液酸神經節苷脂的抗體預處理顯著抑制了2-辛酸誘導的原發性膽汁性膽道炎。由於過去研究認為表現無唾液酸神經節苷脂的細胞為自然殺手細胞 (natural killer cells, NK cells)，因此我們利用先天性缺少NK細胞 的NFIL3 KO 小鼠排除 NK 細胞對於實驗可能的影響，發現其結果與野生型小鼠相似，顯示了有一群表現無唾液酸神經節苷脂的非NK 細胞參與著2-辛酸誘導的原發性膽汁性膽道炎。接著我們進一步分析表現無唾液酸神經節苷脂的細胞發現，在肝臟除了NK 細胞外還有一群表現無唾液酸神經節苷脂的CD8 T 細胞，證實了表現無唾液酸神經節苷脂之肝臟駐留CD8 T細胞對於原發性膽汁性膽道炎扮演著重要的角色。此外，我們發現發病後才給與無唾液酸神經節苷脂抗體無法有效改善病況，這意味著表現無唾液酸神經節苷脂之肝臟駐留CD8 T細胞參與了原發性膽汁性膽道炎的早期發病並影響疾病進展。為了探討這群肝臟駐留CD8 T細胞在原發性膽汁性膽道炎的致病機制，進一步使用流式細胞儀分析，我們發現2-辛酸誘導的原發性膽汁性膽道炎的小鼠發病初期可以看到干擾素γ的產生，並且在抗體預處理可以觀察到產生干擾素γ的細胞群明顯減少。最後，我們使用干擾素γ基因剃除小鼠(IFN-γ knockout mice)來以2-辛酸誘導的膽道炎，發現小鼠膽道周圍免疫細胞浸潤與纖維化的現象顯著改善，證明了表現無唾液酸神經節苷脂之肝臟駐留性CD8 T細胞透過分泌干擾素γ來引發自體免疫性膽道炎。

Primary biliary cholangitis (PBC) is a form of slowly progressive autoimmune hepatitis characterized by a unique serology of antimitochondrial antibody (AMA), pathology of the bile ducts, and liver fibrosis. Previous studies demonstrated that T cells play an important role in the immunopathogenesis of PBC. Recent research has identifiedstudies have found a distinct T cell population known asconsisting of tissue-resident memory (TRM) cells, which are that is critical for nonlymphoid tissue defense against pathogens. In oOur laboratory, we previously discovered that pretreatment with anti-ASGM1 antibodies can inhibit acute hepatitis induced by Concanavalin A (ConA) and PBC induced by 2-octynoic acid (2-OA). Additionally, we found that liver-resident CD8 T cells expressing ASGM1 arewere found to be activated duringin the early stages of ConA-induced acute hepatitis and secrete the pro-inflammatory cytokine interferon-gamma (IFN-γ). However, the specific impact of ASGM1 liver-resident CD8 T cells on the early progression and pathogenesis of PBC has remaineds unclear. The results of this research confirm that pretreatment with anti-ASGM1 antibodies significantly reduces the production of anti-mitochondrial antibodies and IFN-γ in mouse serum. This reduction is associated with decreased expression of IFN-γ and fibrosis-related genes, such as collagen type I and III, as well as a reduction in immune cell infiltration and fibrosis in the bile duct area. These findings demonstrate that the effective inhibition of 2-OA-induced PBC by the administration of anti-ASGM1 antibodiesy effectively inhibits 2-OA induced PBC. Since previous research suggested that cells expressing ASGM1 are natural killer (NK) cells, we used NFIL3 knockout mice, which lack NK cells, to exclude any potential influence of NK cells on the experiment. Interestingly, the results obtained from NFIL3 KO mice were similar to those from wild-type mice, indicating the involvement of non-NK cells expressing ASGM1 in 2-OA-induced PBC. Furthermore, further analysis of ASGM1-expressing cells in the liver revealed the presence of CD8 T cells in addition to NK cells, . This confirmings the significant role played by ASGM1+ liver-resident CD8 T cells in the development of primary biliary cholangitis. Additionally, we observed that post-disease administration of anti-ASGM1 antibodies failed to effectively improve the condition, suggesting. This suggests that ASGM1+ liver-resident CD8 T cells are involved in the early onset of primary biliary cholangitis and influence disease progression. To investigate the pathogenic mechanisms of these liver-resident CD8 T cells in primary biliary cholangitis, we performed further analysis using flow cytometry was performed. We found an increase in IFN-γ productionthat during the initial stages of 2-OA-induced PBC in mice, there was an increase in IFN-γ production, which was significantly reduced withupon antibody pretreatment. Finally, we used IFN-γ knockout mice to induce cholangitis with 2-OA and observed a significant improvement in immune cell infiltration and fibrosis in the bile duct area. This confirms that ASGM1+ liver-resident CD8 T cells mediate 2-OA-induced cholangitis through the secretion of IFN-γ.