2型固有淋巴细胞与CD4+T细胞相互作用调控RSV急性哮喘--固有免疫细胞与适应性免疫细胞对话新视角

Type 2 innate lymphoid cells (ILC2s), which are characterized by the absence of lineage markers (Lin-) and by expression of Sca-1, c-Kit, Thy1.2 and the IL-33 receptor ST2, are a critical source of type 2 cytokines and play an important role in initiating airway hyperresponsiveness and airway inflammation. However, up to now, little is known about the interactions between ILC2s and other immune cells, particularly Th cells for the development of asthma. By using a murine model of RSV-induced acute asthma, we found that infection of BALB/c mice with respiratory syncytial virus (RSV) can induce an increase in the absolute number of ILC2s as well as IL-13-producing ILC2s in the lungs of mice, particularly at day 3 and day 7 after infection. Adoptive transfer of pulmonary ILC2s elicited an augmented expression of IL-13 mRNA, following a massive infiltration of eosinophils in the lungs of transferred mice, demonstrating that pulmonary type 2 innate lymphoid cells may act as a promoter for RSV-induced airway inflammation. It is interesting that the number of ILC2s in the lungs of Rag2-/- mice, that lack both T cells and B cells, was reduced significantly during RSV infection. However, adoptive transfer of CD4+T cells into Rag2-/- mice can reconstitute the number of pulmonary ILC2s. On the other hand, the expression of mRNA for IL-5 and IL-13 was diminished markedly in pulmonary CD4+T cells which were isolated from RSV-infected ILC2s-deficient mice, suggesting that there are possible interactions or “cross talk” between type 2 innate lymphoid cells and CD4+T cells in RSV-induced acute asthma. . In the present study, we use established experimental mouse model in which we infected mice with respiratory syncytial virus and examine the development of acute AHR and airway inflammation. We are interested in: ①whether pulmonary ILC2s and CD4+T cells cooperate to mediate RSV-induced acute asthma; ②which cytokines and molecules are associated with the interactions or “cross talk” between ILC2s and CD4+T cells; ③how the molecules regulate activation, proliferation and differentiation of ILC2s and CD4+T cells for the development of RSV-induced acute asthma. This study may lead to improved therapies for non-allergic forms of asthma triggered by viral infection.

作为Th2型细胞因子的重要来源细胞，2型固有淋巴细胞(ILC2)在哮喘发生中的作用及地位受到关注。利用RSV感染诱发的急性哮喘鼠模型，我们发现肺ILC2不仅是参与RSV哮喘的重要免疫细胞，其更可能与CD4+T细胞之间存在相互作用。实验结果显示，与适应性应答完整存在的BALB/c鼠相比，感染RSV的Rag2-/-鼠肺ILC2数量明显减少，但过继回输CD4+T细胞可恢复其肺ILC2数量；缺乏ILC2则导致RSV哮喘鼠CD4+T细胞IL-5、IL-13产生能力下降，推测在RSV哮喘发生中存在ILC2与CD4+T细胞的相互作用或“cross talk”。本项目旨在证实肺ILC2与CD4+T细胞通过相互作用调控RSV哮喘，揭示介导细胞间相互作用的关键蛋白分子，探讨其在细胞活化、增殖以及分化中的作用及作用机理，为开发研制针对哮喘，尤其是病毒感染诱发的非过敏性哮喘的治疗新药及临床治疗提供新思路和新靶标。

具有强大的Th2型细胞因子分泌能力的2型固有淋巴细胞（Type 2 innate lymphoid cells, ILC2s）及CD4+Th2细胞是介导过敏性哮喘的重要效应细胞。但在由病毒感染诱发的非过敏性哮喘，尤其是最为常见的由呼吸道合胞病毒（Respiratory syncytial virus, RSV）感染诱发的急性非过敏性哮喘中，ILC2s及CD4+T细胞是否参与其中，且二者之间是否存在相互作用，目前尚不清楚。通过本项目研究，我们证实了ILC2s与CD4+T细胞同为RSV急性哮喘的重要效应细胞。肺组织内ILC2s可通过分泌大量的Th2型细胞因子，尤其是IL-5和IL-13介导RSV急性哮喘；而阻断CD4+T细胞则明显降低RSV气道炎症应答。RSV感染诱导的肺ILC2s扩增与活化部分依赖于CD4+T细胞。CD4+T细胞来源的IL-2对RSV急性哮喘鼠肺ILC2s的扩增及其Th2型细胞因子分泌至关重要。ILC2s亦可影响肺CD4+T细胞生物学活性。过继回输肺ILC2s明显提高RSV急性哮喘鼠肺CD4+T细胞数量及其细胞因子分泌水平。ILC2s表达的膜分子OX40L与CD4+T细胞表达的OX40相结合，可能是ILC2s诱导CD4+T细胞活化与增殖的重要途径。有趣的是预先RSV感染可一定程度上减轻变应原OVA诱发的过敏性哮喘，降低气道炎症和嗜酸细胞肺浸润。该现象可能与RSV感染改变了肺ILC2s生物学活性有关。. 本研究项目在国家自然科学基金委的资助下，自2017年1月1日开始至2020年12月31日结束，共发表SCI学术论文5篇，中文核心期刊论文2篇，培养博、硕士研究生7人，按预定计划圆满完成课题预定目标。

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