探討invariant NKT細胞在原發性膽道硬化症之角色

Study on the Role of Invariant NKT Cells in Primary Biliary Cirrhosis

章肇軒(Chao-Hsuan Chang)

指導教授 ： 莊雅惠

國立臺灣大學/醫學院/醫學檢驗暨生物技術學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.02850

摘要

原發性膽道硬化症 (primary biliary cirrhosis；PBC) 為肝臟特異性之自體免疫疾病，特徵為患者肝內膽道上皮細胞遭受破壞致使膽汁鬱積及淋巴浸潤於門脈區，且血清中含高量之抗粒線體自體抗體(AMAs)。iNKT細胞可辨識抗原呈獻細胞上CD1d分子所呈獻之醣脂類抗原，迅速活化後分泌大量細胞激素引起下游免疫反應。本實驗室曾利用xenobiotic (2-OA-BSA) 致敏之PBC小鼠模式，在2-OA-BSA致敏前18~20小時給予α-Galactosylceramide (α-GalCer)活化iNKT細胞，發現小鼠肝臟中CD8+ T細胞數目明顯增加，血清中AMAs效價與肝臟門脈及膽道區域破壞情況上升，且肝臟有纖維化情形。在此，我們進一步研究iNKT細胞之存在與否或是否受外源性醣脂類抗原活化對PBC疾病進程之影響。
在本研究中，我們使用外源性醣脂類抗原，α-GalCer，活化iNKT細胞，觀察2-OA-BSA致敏之PBC小鼠病理變化。結果顯示，小鼠在同時給予α-GalCer及2-OA-BSA致敏後可使其血清中細胞激素迅速上升，且最終可觀察到小鼠之PBC疾病病徵加重，表示當iNKT細胞被活化後，能加速疾病進程；此外，我們亦使用缺乏iNKT細胞之CD1d-/-小鼠與正常小鼠，單獨以2-OA-BSA致敏並觀察PBC進程。結果顯示CD1d-/-小鼠亦可產生門脈區淋巴浸潤及血清中AMAs效價上升等PBC疾病病徵，且相較於同以2-OA-BSA致敏之正常小鼠並無明顯差異。
此結果說明，當缺乏外源性醣脂類物質活化iNKT細胞時，iNKT細胞對於推進PBC疾病進程影響甚小，反之，若給予α-GalCer強力刺激後，活化之iNKT細胞可分泌大量細胞激素，促進肝臟內免疫細胞數目及功能提升，加速淋巴浸潤及膽道破壞，並促使肝臟出現纖維化，加重PBC疾病。
在本研究中，我們使用外源性醣脂類抗原，α-GalCer，活化iNKT細胞，觀察2-OA-BSA致敏之PBC小鼠病理變化。結果顯示，小鼠在同時給予α-GalCer及2-OA-BSA致敏後可使其血清中細胞激素迅速上升，且最終可觀察到小鼠之PBC疾病病徵加重，表示當iNKT細胞被活化後，能加速疾病進程；此外，我們亦使用缺乏iNKT細胞之CD1d-/-小鼠與正常小鼠，單獨以2-OA-BSA致敏並觀察PBC進程。結果顯示CD1d-/-小鼠亦可產生門脈區淋巴浸潤及血清中AMAs效價上升等PBC疾病病徵，且相較於同以2-OA-BSA致敏之正常小鼠並無明顯差異。
此結果說明，當缺乏外源性醣脂類物質活化iNKT細胞時，iNKT細胞對於推進PBC疾病進程影響甚小，反之，若給予α-GalCer強力刺激後，活化之iNKT細胞可分泌大量細胞激素，促進肝臟內免疫細胞數目及功能提升，加速淋巴浸潤及膽道破壞，並促使肝臟出現纖維化，加重PBC疾病。

關鍵字

原發性膽道硬化症 ； iNKT細胞 ； α-GalCer ； 2-OA BSA致敏小鼠 ； CD1d-/- 小鼠

並列摘要

Primary biliary cirrhosis (PBC) is a liver specific autoimmune disease. It is characterized by progressive inflammatory destruction of intrahepatic bile ducts which results in cholestasis and may progress to cirrhosis and liver failure. The most characteristic feature of PBC is the presence of AMAs in the serum. Invariant natural killer (iNKT) cells are restricted to CD1d molecules on antigen-presenting cells and recongized lipids and glycolipids as antigens, such as α-Galactosylceramide (α-GalCer). When NKT cells are stimulated, they are capable to rapidly produce large amounts of cytokines to exert effector functions and immunoregulatory functions. Our previous study using xenobiotic (2-OA-BSA) -induced PBC mouse model demonstrated that activation of iNKT cells by α-GalCer administration prior to 2-OA-BSA immunization could exacerbate the progression of PBC, including increased AMAs production, portal inflammation, increased number of CD8+ T cells in liver, and the formation of liver fibrosis. In this study, we investigated the existence of NKT cells or the administration of exogenous glycolipids to activate iNKT cells in the progression of PBC.
For this purpose, we injected exogenous glycolipids, α-GalCer, and 2-OA-BSA at the same time to mice . After injection of α-GalCer, the elevated serum levels of IFN-γ and IL-4 were revealed, and finally, the exacerbation of PBC pathogenesis were observed. These results suggested that the activation of iNKT cells is important in promoting PBC progression. However, 2-OA-BSA immunized CD1d-/- mice, which lack the receptor required for NKT cell development, also developed the symptom of PBC, such as the lymphocyte infiltration in the portal area in liver, and detectable AMA titers in the serum. Compared to normal mice, there were no significant differences in the severity of disease progression in CD1d-/- mice.
In conclusion, our results demonstrated that while the absence of exogenous glycolipids, such as α-GalCer, iNKT cells play a slightly effects in PBC progression, whereas strongly activated by α-GalCer stimulation, iNKT cells could secrete copious amounts of cytokines to elicit the elevated number or function of immune cells in the liver to accelerate liver damage.

並列關鍵字

primary biliary cirrhosis ； iNKT cells ； α-GalCer ； 2-OA BSA-induced PBC mouse model ； CD1d-/- mice

參考文獻

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