Regulation of TH2 memory/effector cells during allergic inflammation

描述（由申请人提供）：临床和实验研究表明，过敏原特异性TH2记忆/效应细胞存在于肺部，并有助于哮喘的持续和进展。最近，CD4+TH17细胞在变应性炎症调节中的病理作用已被确定；然而，在TH2免疫反应的背景下可以分泌IL-17的细胞类型仍然是难以捉摸的。我们发现了一种新的人类TH2记忆/效应细胞亚群，其特征是同时产生TH17和TH2细胞因子以及GATA3和ROR？单细胞水平T共表达；称为IL-17-TH2细胞。与人类的研究结果相呼应，IL-17-TH2细胞主要存在于发炎的肺部，而不存在于其他淋巴器官中，并且在过敏性肺部疾病小鼠模型中，IL-17-TH2细胞在气道炎症的慢性阶段仍然是主要的产生il -17的T细胞。此外，我们发现细胞因子IL-12和IL-21能够诱导IL-17和IL-21，同时促进TH2记忆/效应细胞产生TH2细胞因子。用IL-12处理TH2记忆/效应细胞可诱导干扰素调节因子4 （IRF4）显著上调，IRF4是TH2和TH17免疫应答发展的关键因子。这些发现表明，CD4+TH2记忆/效应细胞存在大量的可塑性，这可以通过局部炎症线索控制。值得注意的是，我们观察到特应性哮喘患者血液中总CD4+TH2记忆/效应细胞池中循环IL-17-TH2细胞的频率显著升高。在小鼠中，我们证明了抗原特异性IL-17-TH2细胞与仅由经典TH2或TH17细胞诱导的细胞相比，可引发炎症性白细胞的大量涌入、杯状增生和粘蛋白的产生。总的来说，这些初步研究导致我们的中心假设，IL-12和IL-21诱导肺常驻CD4+ TH2记忆/效应细胞获得TH17炎症特性，并且这种产生的IL-17-TH2细胞有助于慢性过敏性哮喘的恶化。在Aim 1中，我们专注于确定IL-12诱导IL-17-TH2细胞的潜在机制。我们假设IL-12诱导TH2记忆/效应细胞中IRF4的上调，从而导致IL-17和IL-21细胞因子的产生。在Aim 2中，我们将确定IL-21在调节IL-17-TH2细胞的诱导和功能中的作用。我们假设自分泌IL-21与IL-12协同作用，增强IL-17-TH2细胞的诱导和效应功能。在Aim 3中，我们将定义IL-17-TH2细胞在慢性过敏性哮喘免疫发病机制中的生物学相关性。我们假设IL-17-TH2细胞触发多种趋化因子的产生，导致慢性过敏性哮喘期间肺部异质炎性白细胞的浸润和病理改变。我们相信本研究将拓宽我们对IL-17-TH2细胞炎症特性的认识，以及IL-17-TH2、经典TH2和TH17细胞在慢性变应性炎症中的相互关系，从而为哮喘和特应性的治疗提供更有针对性的方法。

DESCRIPTION (provided by applicant): Clinical and experimental investigations suggest that allergen-specific TH2 memory/effector cells reside in the lung and contribute to the persistence and progression of asthma. Recently, a pathological role for CD4+TH17 cells in the regulation of allergic inflammation has been identified; however, the cell types that can secrete IL-17 within the context of TH2 immune responses remain elusive. We have discovered a novel subset of human TH2 memory/effector cells featuring concurrent TH17 and TH2 cytokine production and GATA3 and ROR?t co-expression at a single cell level; termed IL-17-TH2 cells. Mirroring the findings in humans, IL-17-TH2 cells could be found primarily in inflamed lung, but not other lymphoid organs, and persist as the dominant IL-17-producing T cells at the chronic stage of airway inflammation in a mouse model of allergic lung diseases. Furthermore, we found that the cytokine IL-12 and IL-21 are capable of inducing IL-17 and IL-21, while promoting TH2 cytokine production by TH2 memory /effector cells. The treatment of TH2 memory/effector cells with IL-12 induces a significant up-regulation of IRF4 (interferon regulatory factor 4), a critical factor for the development of TH2 and TH17 immune responses. These findings suggest that substantial plasticity exists within CD4+TH2 memory/effector cells and this can be controlled by local inflammatory cues. Notably, we observed that the frequency of circulating IL-17-TH2 cells within total CD4+TH2 memory/effector cell pool is significantly elevated in blood of patients with atopic asthma. In mouse, we demonstrated that antigen specific IL-17-TH2 cells triggered much prominent influx of inflammatory leukocytes, goblet hyperplasia and mucin production compared with those induced only by classical TH2 or TH17 cells. Collectively, these preliminary studies lead to our central hypothesis that IL-12 and IL-21 induce lung resident CD4+ TH2 memory/effector cells to acquire TH17 inflammatory properties, and that such generated IL-17-TH2 cells contribute to the exacerbation of chronic allergic asthma. In Aim 1, we focus on determining the underlying mechanisms by which IL-12 induce IL-17-TH2 cells. We hypothesize that IL-12 induces up-regulation of IRF4 in TH2 memory/effector cells, leading to IL-17 and IL-21 cytokine production. In Aim 2, we will determine the role of IL-21 in regulating the induction and function of IL-17-TH2 cells. We hypothesize that autocrine IL-21 synergizes with IL-12 to enhance the induction and effector function of IL-17-TH2 cells. In Aim 3, we will define the biological relevance of IL-17-TH2 cells in the immunopathogenesis of chronic allergic asthma. We hypothesize that IL-17-TH2 cells trigger diverse chemokine production, leading to the infiltration of heterogeneous inflammatory leukocytes and pathological changes in lung during chronic allergic asthma. We believe that the proposed studies will broaden our views of the inflammatory properties of IL-17-TH2 cells and the inter-relationship between IL-17-TH2, classical TH2 and TH17 cells during chronic allergic inflammation, and thus provide more specific approaches for the treatments in asthma and atopy. PUBLIC HEALTH RELEVANCE: The goal of this project is to determine the underlying mechanisms that regulate the induction and function of a novel IL-17-producing TH2 memory/effector cell subset and define their biological relevance in the immunopathogenesis of chronic allergic inflammation. By examining this novel TH2 memory/effector cell subset, we will learn how the proinflammatory cytokines modulate tissue resident TH2 memory/effector cells to acquire distinctive inflammatory properties and understand the inter-relationship between TH2 and TH17 cells, that contribute to the heterogeneity, persistence and severity of chronic allergic asthma.