探討IL-30於原發性膽汁性膽管炎之免疫調控作用

Abstract

原發性膽汁性膽管炎(Primary biliary cholangitis, PBC)是一個肝臟慢性自體免疫疾病，在我們先前的研究中發現將攜帶IFN-γ基因的Adeno-associated virus (AAV)給予小鼠的同時誘發小鼠產生PBC，在疾病早期與對照組小鼠相比發炎程度升高很多，但在疾病晚期可能因為Interlukin-30 (IL-30)的上升使IFN-γ造成的疾病嚴重程度趨緩，因此推論IL-30在PBC小鼠中可能具有免疫抑制功能。IL-30，是IL-27的次單元體，又稱為IL-27p28，其他研究指出IL-30可以減緩肝臟發炎所造成的損傷與纖維化。因此在本研究中我們將AAV-mIL-30打入2-OA-OVA誘發的PBC小鼠模式，探討IL-30在原發性膽汁性膽管炎中是否具有免疫抑制功能。首先，我們使用已被廣泛研究的conA誘發之急性肝損傷小鼠模型確認AAV-mIL-30在體內的免疫抑制能力，發現給予AAV-mIL-30的急性肝損傷小鼠其血清中的IFN-γ與IL-12與對照組小鼠相比明顯降低，顯示AAV-mIL-30在體內確實有免疫抑制的能力。在PBC中，我們使用2-OA-OVA誘發小鼠產生PBC後三週再給予AAV-mIL-30，兩週後分析肝臟浸潤免疫細胞的數目與功能，發現IL-30可以降低CD4+ T細胞的活化與IFN-γ的分泌，且抗原呈獻細胞的功能被抑制，而CD4+ Foxp3+ 調節性T細胞數目增加，因此我們認為IL-30是透過抑制抗原呈獻細胞與增加調節性T細胞來達到抑制T細胞的效果。另外，我們也發現在給予AAV-mIL-30小鼠肝臟中類鐸受體(Toll-like receptor, TLR)的表現量下降。而在11週PBC小鼠中我們發現給予AAV-mIL-30小鼠相較於對照組小鼠，肝臟中第一型纖維蛋白的表現量下降，但是肝臟門脈區淋巴細胞浸潤的情形並沒有被減緩。由以上實驗結果顯示IL-30在PBC中可以抑制T細胞的活化與分泌IFN-γ的能力，且可以增加調節性T細胞。

Primary biliary cholangitis (PBC) is a chronic liver autoimmune disease. Our previous study found that PBC mice administered with adeno-associated virus-expressing IFN-γ (AAV-IFN-γ) showed a severe disease performance in early phase but subsequently led to downregulation of chronic inflammation with an increase of interleukin-30 (IL-30). IL-30, also called IL-27p28, has been shown to attenuate liver injury and fibrosis. In this study, we investigated whether IL-30 had an immunosuppressive function in PBC by administering mouse IL-30 expressing AAV (AAV-mIL-30) to 2-OA-OVA immunized PBC mice. At first, we defined the immunosuppressive function of AAV-mIL-30 in vivo by a well-known conA-induced hepatitis mouse model. The results showed that serum levels of IFN-γ and IL-12 were decreased in AAV-mIL-30 receiving conA induced hepatitis mice, indicating that AAV-mIL-30 had an immunosuppressive function in vivo. In PBC, the expression of CD25 and IFN-γ secretion in CD4+ T cells were decreased in mice administered with AAV-mIL-30 three weeks post 2-OA-OVA immunization. The suppressive function of IL-30 might be due to the increase the frequency of CD4+Foxp3+ regulatory T cells and inhibition of the function of antigen presenting cells. In addition, we also found the expression of toll-like receptors (TLRs) in liver was decreased in AAV-mIL-30 receiving PBC mice. Moreover, the type I collagen production was decreased while the lymphocytes infiltration in portal area was not changed in AAV-mIL-30 injected mice 11 weeks post 2-OA-OVA immunization. These results suggested that IL-30 could suppress the function of T cells and increase the number of Tregs in PBC.