Tim3/Galectin-9途径在大鼠肝移植免疫耐受诱导中的作用及机制

T cell immunoglobulin domain and mucin domain-3 (Tim3) and its legand Galectin-9 have more intensive and powerful inhibitory effect on immune regulation than other co-stimulate factors of B7 famliy. Macrophages with high expression of Galectin-9 have strong inhibitory effect ont only on native T cells, but also on actived effector T cells. It only induces the aggregation and apoptosis of Th1 cells, and almost did not affect Th2 cells. That implys Tim3/Galectin-9 pathway could play an importatant role in the induction of immune tolerance. However, the exactly role of this pathway in the immunoterance induction of liver transplantaton remains unclear. Our previous studies have found that Kupffer cell plays an importatant role in the immunoterance induction of liver transplantation in rats.But the detailed mechanisms are still unclear. In the project, the Kupffer cell is chosen as the target cell, the expression of Tim3/Galectin-9 pathway is blocked and enhanced by shRNA interference to explore its effect on proliferation and function of T cell, to elucidate its role in immunoterance induction of rat liver transplantation and do some exporalory work for using this pathway to induce immune tolerance in liver transplanatation.

与其它B7共刺激途径相比，T细胞免疫球蛋白粘蛋白3（Tim3）及其配体半乳凝集素-9（Galectin-9）途径具有更广泛、更强大的免疫抑制作用。巨噬细胞通过高表达Galectin-9，不仅对初始T细胞具有强大的抑制作用，而且对已致敏的效应性T细胞的功能也有重要调节作用。其仅诱导Th1细胞聚集和凋亡，而Th2细胞几乎不受影响，提示其在移植免疫耐受的诱导过程中可能具有重要作用。然而，该途径在肝移植免疫耐受中的作用机制尚不清楚。我们前期研究发现，肝脏内特殊巨噬细胞Kupffer细胞在大鼠肝移植免疫耐受的诱导过程中起重要作用，但机制并不完全清楚。本项目以Kupffer细胞为靶细胞，从信号转录和基因调控的角度出发，通过阻断或增强其表达，从而了解该途径通过Kupffer细胞对T细胞增殖和功能的具体影响及可能机制，阐明其对大鼠肝脏移植免疫耐受的调节作用，为利用其诱导肝脏移植免疫耐受作一些探索性研究。

我们的前期研究发现肝脏中的 Kupffer 细胞在大鼠肝移植免疫耐受的诱导过程中起重要作用，但机制并不完全清楚。本项目选择 Kupffer 细胞为靶细胞，从信号转录、基因调控和蛋白表达的角度出发，观察T细胞免疫球蛋白粘蛋白3（Tim3）及其配体半乳凝集素-9（Galectin-9）途径是否通过Kupffer 细胞调节淋巴细胞增殖和功能。研究发现：增强galectin-9的表达可显著抑制T-bet、ROR-γt和IFN-γ、IL-17 mRNA的表达水平，受体的生存时间明显延长，证实了其对Th1及Th17细胞的负性调控从而明显抑制急性排斥反应的发生。体外实验进一步证实：galectin-9不仅可以直接作用于淋巴细胞，抑制淋巴细胞增殖活化，并促进其凋亡；还可能通过调节肝脏内Kupffer细胞因子的表达进而抑制淋巴细胞的功能，并抑制急性排斥反应。由此表明，galectin-9对淋巴细胞的功能起着负性调节作用，并在肝脏移植免疫耐受的形成过程中起重要作用。采用有效手段适时适度的调控galectin-9的表达可能成为避免肝脏移植急性排斥反应，甚至诱导免疫耐受的新方法。