Translational studies of the induction and functional role of Th2 polarized CD4+ T-cells in chronic liver damage and hepatic fibrogenesis

免疫机制在肝脏炎症和随后的纤维化和肝硬化中起关键作用。广泛的研究表明，先天免疫系统和适应性免疫系统的细胞成分的浸润和局部激活是纤维化级联反应启动的先决条件。这与临床相关，因为尽管迫切需要有效的抗纤维化治疗，但治疗选择仍然有限。对肺等其他器官的研究表明，CD4+ t辅助细胞的Th2极化与重塑过程直接相关。在器官纤维化过程中，典型的Th2细胞因子包括IL-4和IL-13激活间充质细胞，合成大量的细胞外基质化合物。因此，薄壁组织逐渐被结缔组织所取代，最终导致器官衰竭。此外，th2细胞可以通过细胞间相互作用诱导交替活化的M2巨噬细胞，也显示出纤维化特性，从而进一步放大器官纤维化。然而，对于th2 -纤维化模式是否也适用于肝脏，人们仍然知之甚少。有强有力的证据表明，th2极化的CD4+ t细胞在寄生性肝病中起关键作用，但它们在无菌、抗原非依赖性肝脏炎症中的作用尚不明确。本研究的目的是分析肝纤维化不同阶段t辅助细胞的分化，并在描述性和功能性研究中检查它们对基质沉积的贡献。在具有不同潜在病因的病变外植肝脏组织标本的全面收集的帮助下，将有可能精确表征肝纤维化中肝内t细胞谱和局部免疫环境。用原代人细胞进行的体外细胞培养试验将有助于研究肝脏募集和局部诱导Th2分化的t辅助细胞的机制。分析CD4+ t细胞与肝脏驻留实质细胞和非实质细胞之间的相互作用将是该项目人体部分的主要重点。所得结果将在实验性抗原非依赖性肝纤维化模型中得到验证。在纤维形成过程中的特定时间点，浸润t细胞的特征将被表征。敲除Th2关键成分遗传缺陷的动物将有助于研究这种免疫反应在肝纤维化中的功能相关性。如果这些动物表现出较少的纤维化，CD4+ t细胞的过继性转移计划揭示是这类细胞还是先天免疫系统的成员，如先天淋巴样细胞或nkt细胞，它们也可以分泌th2相关的细胞因子，本质上促进肝纤维化。通过促进我们对肝纤维化发病机制的理解，该项目可能有助于开发新的治疗工具来对抗肝硬化。

Immune mechanisms are critically involved in liver inflammation and subsequent fibrogenesis and cirrhosis. Extensive research has unravelled that the infiltration and local activation of cellular components of the innate as well as the adaptive immune system are prerequisites for the initiation of profibrotic cascades. This is clinical relevant because the therapeutical options are still limited despite the urgent need for effective antifibrotic treatments. Studies in other organs such as the lung have shown that the Th2 polarization of CD4+ T-helper cells is directly linked to remodeling proceses. During organ fibrosis prototypical Th2 cytokines including IL-4 and IL-13 activate mesenchymal cells which synthesize abundant amounts of extracellular matrix compounds. As a consequence, parenchyma is gradually replaced by connective tissue eventually leading to organ failure. Furthermore, Th2-cells can induce alternatively activated M2 macrophages ,that also display profibrotic properties, through cell-cell interaction, whereby organ fibrosis is further amplified. However, it is still widely unknown, whether the Th2-fibrosis paradigm also applies to the liver. There is robust evidence that Th2-poalrized CD4+ T-cells are critically involved in parasitic liver diseases, but their role in sterile, antigen-independent liver inflammation remains elusive. Aim of this proposed translational project is to dissect the differentiation of T-helper cells at different stages of liver fibrosis and to examine their contribution to matrix depostion in descriptive and functional studies. With the help of a comprehensive collection of tissue specimens of explanted diseased liver with different underlying etiologies, it will be possible to precisely characterize intrahepatic T-cell profiles and the local immune environment in liver fibrosis. In vitro cell-culture assays with primary human cells will allow to study mechanisms of hepatic recruitment and local induction of Th2 differentiated T-helper cells. The analysis of the reciprocal interplay between CD4+ T-cells and liver-resident parenchymal and non-parenchymal cells will be a major focus in the human part of this project. The obtained findings will be validated in experimental antigen-independent liver fibrosis models. At defined time points during fibrogenesis the signature of infiltrating T-cells will be characterized. Knockout animals with a genetic deficiency of Th2 key components will serve to study the functional relevance of this immune response in liver fibrosis. If these animals exhibit less fibrosis adoptive transfer of CD4+ T-cells is planned to unravel whether this cell class or members of the innate immune system, such as innate lymphoid cells or NKT-cells, which can also secrete Th2-related cytokines, essentially booster heptic fibrogenesis. By promoting our understanding of the pathogenesis of liver fibrosis this project may help to develop novel therapeutic tools to combat liver cirrhosis.