Regulation and role of GM-CSF production by human T helper cells in health and inflammation

辅助性T细胞代表了一个不断增长的特化免疫细胞亚群家族，它们在细胞因子谱、迁移特性和抗原靶点方面存在差异。近年来，Th17细胞作为辅助性T细胞谱系加入了这个家族，在自身免疫中具有主要的致病功能。我们最近已经证明存在两种类型的人类Th17细胞具有促炎性和抗炎性细胞因子谱。抗炎Th17细胞共同产生IL-10，而促炎Th17细胞共同产生ifn - γ。它们不仅在功能上存在差异，而且在引物要求和病原体特异性上也存在差异。这些发现揭示了Th17细胞亚群中意想不到的异质性，并暗示了它们在健康和疾病中的作用。GM-CSF最近被确定为多发性硬化症实验性自身免疫性脑脊髓炎（EAE）小鼠模型中自身免疫的Th17细胞系的关键致病细胞因子。它甚至被证明与EAE的发病机制比IL-17更相关，IL-17迄今被认为是Th17的特征细胞因子。这表明Th17细胞衍生的GM-CSF是炎症设置的有希望的治疗靶点。然而，其在人类辅助性T细胞中的表达、调控及其在健康和疾病中的作用尚未被研究。考虑到其在小鼠中的致病作用，详细表征GM-CSF在人T细胞中的调控将为制定治疗靶向策略提供重要的科学依据。因此，我们的目标是鉴定和表征人体内产生GM-CSF的T辅助细胞。我们的初步数据表明，GM-CSF可以独立于IL-17和任何其他谱系定义细胞因子（如ifn - γ， IL-4）在T辅助细胞中表达。这表明存在只产生gm - csf的T辅助细胞。我们将研究它们的生成条件、稳定性和可塑性、迁移特性以及人类T辅助细胞中GM-CSF产生的转录调控。我们还将分析产生GM-CSF的T辅助细胞的TCR库是否与Th1、Th2和Th17细胞亚群的TCR库不同，方法是使用扩增的T细胞库对人类TCR库进行大规模查询。这种方法是基于抗原特异性T辅助细胞对病原体衍生抗原和自身抗原的增殖反应。这些研究将首次提供人类产生GM-CSF的T辅助细胞的特征，并将确定是否存在与经典T辅助亚群不同的具有独特功能和表型特性的专门的GM-CSF产生亚群。该项目将为该细胞因子在感染和自身免疫性疾病中的靶向治疗提供科学依据。

T helper cells represent a growing family of specialized immune cell subsets that differ in their cytokine profile, migration properties and antigen targets. Th17 cells joined this family as a T helper cell lineage with major pathogenic functions in autoimmunity a few years ago. We have recently demonstrated the existence of two types of human Th17 cells with pro- and anti-inflammatory cytokine profiles. Anti-inflammatory Th17 cells co-produced IL-10 whereas pro-inflammatory Th17 cells co-produced IFN-gamma. They not only differed in function but also in priming requirements and pathogen specificities. These findings have revealed unexpected heterogeneity within the Th17 cell subset with implications for their role in health and disease.GM-CSF has recently been identified as a crucial pathogenic cytokine of the Th17 cell lineage for autoimmunity in the experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis. It has even been shown to be more relevant for EAE pathogenesis than IL-17, which has so far been considered the Th17 signature cytokine. This suggests Th17 cell derived GM-CSF to be a promising therapeutic target in settings of inflammation. However, its expression, regulation and role in human T helper cells in health and disease have not been studied. Considering its pathogenic role in mice, a detailed characterization of GM-CSF regulation in human T cells will be important to provide a scientific basis for therapeutic targeting strategies. We therefore aim to identify and characterize GM-CSF producing T helper cells in humans. Our preliminary data demonstrate that GM-CSF can be expressed in T helper cells independently of IL-17 and also of any other lineage defining cytokine such as IFN-gamma, IL-4. This suggests the existence of GM-CSF-only producing T helper cells. We will study the requirements for their generation, their stability and plasticity, their migration properties as well as the transcriptional regulation of GM-CSF production in human T helper cells. We will also analyze whether the TCR repertoire of GM-CSF producing T helper cells differs from that of Th1, Th2 and Th17 cell subsets by using a novel method that allows the large-scale interrogation of the human TCR repertoire by using libraries of amplified T cells. This approach is based on the proliferation of antigen specific T helper cells in response to pathogen derived antigens and autoantigens. These studies will for the first time provide a characterization of human GM-CSF producing T helper cells and will determine whether a specialized GM-CSF producing subset with unique functions and phenotypic properties that differs from the classical T helper subsets exists. The proposed project will provide a scientific basis for therapeutic targeting of this cytokine in infections and autoimmune diseases.