肺脏来源exosomes在维持呼吸道免疫耐受中的作用及相关机制研究

A vast quantity of environmental antigens settle upon the respiratory mucosal surface and challenge the immune system, but respiratory immune system always maintain a dynamic balance, which suggest that there are fine regulations in respiratory immune system. Exosomes are nano-scale vesicles released from all kinds of live cells, which have a structure of lipid bi-layer. Exosomes expressing TGF-β1 are potently immunosuppressive and can induce immunotolerance. We found that exosomes from lungs of mice (L-EXO) expressed high level TGF-β1 and showed immunosuppressive effect in vitro dependent on TGF-β1. Moreover, L-EXO showed significantly preventive effect to mouse asthma. Interestingly, L-EXO from asthmatic mouse possessed more TGF-β1 than that from normal mouse. In conclusion, we assume that L-EXO play an important role in the maintenance of respiratory immune balance. In this project, we will illustrate whether L-EXO are involved in the maintenance of respiratory immune balance. First, we will study the mechanism of L-EXO to alleviate the asthma. Then we will detect whether the mice show exacerbating asthmatic symptoms when the physiologic secretion of L-EXO is inhibited. Moreover, we will explore the mechanism of different TGF-β1 expression between L-EXO from asthmatic and normal mice. And their different immunosuppressive effect will also be detected. Our results will uncover a novel mechanism contributing to the respiratory immune balance, therefore, providing new ideals for the therapy of respiratory diseases caused by imbalance of immune system.

呼吸道是重要的免疫耐受场所，对大量的外来吸入抗原不产生强烈的免疫应答，而人们对呼吸道如何维持免疫耐受状态知之甚少。Exosomes是各种活细胞分泌的膜性囊泡，表达TGF-β1的exosomes具有免疫抑制效应，可诱导机体免疫耐受。我们发现，小鼠肺来源exosomes (L-EXO)表达高水平TGF-β1，能依赖TGF-β1发挥免疫抑制功能。此外，L-EXO对哮喘小鼠有明显预防效果。更有趣的是，哮喘与正常小鼠L-EXO相比，表达更高水平的TGF-β1。这些结果预示，L-EXO在维持呼吸道免疫耐受中发挥重要作用。本项目将通过抑制生理状态下L-EXO的分泌后观察小鼠哮喘症状，对比哮喘与正常小鼠L-EXO功能差异，从而进一步明确L-EXO在维持呼吸道免疫耐受中的作用。此外，我们还将对相关机制进行探讨。该项目研究结果将揭示呼吸道维持免疫耐受的一种新机制，从而为呼吸道免疫失衡疾病的治疗提供理论指导。

呼吸道免疫平衡受到机体严格调控。据报道，胞外囊泡（EVs）参与维持肠道的免疫平衡。胞外囊泡是否参与了呼吸道免疫平衡的调节有待揭示。在这项研究中，我们发现从小鼠肺脏中分离出来生理的胞外囊泡含有免疫抑制细胞因子TGF-β1和IL-10。在L-EV众多亚型中，只有CD8α+ CD11c+ EV亚型是TGF-β1和IL-10阳性。此外，只有CD8α+ CD11c+ EV亚群通过TGF-β1体外抑制CD4+ T细胞增殖，缓解小鼠哮喘疾病症状。机制上，L-EVs以TGF-β1和IL-10依赖性的方式有效地抑制OVA抗原特异性CD4+ T细胞增殖。此外，L-EVs通过IL-10抑制肺门淋巴结的CD4+ T细胞分泌IL-4，IL-9和IL-17A，提示L-EVs抑制Th2，Th9和Th17细胞的免疫应答。总之，我们的研究结果表明，来自肺部的胞外囊泡参与呼吸道免疫平衡的维持，这揭示了维持呼吸道免疫动态平衡的新机制。