Role of secreted phospholipase A2 in the activation of human CD1-restricted T cells

项目总结 CD1蛋白在结构上与MHC I类有关，但它们向T细胞递送脂类抗原而不是多肽 细胞。我们和其他人已经证明，识别自身脂质的CD1限制性T细胞在人类中非常丰富 目前尚不清楚这些T细胞的激活在体内是如何被调节的。对……的公开反应 自身脂质提示，必须严格调控抗原性CD1-脂质复合体，以防止连续 T细胞刺激。脂肪酸和溶血磷脂酰胆碱(LPC)都被确定为抗原 人类CD1限制性T细胞。当磷脂酶A2(PLA2)作用于 膜磷脂，支持PLA2活性在产生CD1自身抗原中的作用。自.以来 分泌型磷脂酶A2(SPLA2)是对组织损伤和感染的反应而增加，我们假设sPLA2 人类的活性是调节CD1限制性T细胞激活的常见机制， 通过暂时增加CD1自身脂类抗原的可获得性。这得到了我们初步的支持 正常人抗原提呈细胞上PLA2活性导致CD1依赖性T细胞活化的观察 个人。此外，由于sPLA2水平在许多慢性炎症条件下呈结构性升高， 包括类风湿性关节炎、哮喘、动脉粥样硬化和牛皮癣，这种机制可能是持续性T细胞 在这些条件下，细胞通过持续高水平的自身脂类抗原激活。在本提案中，我们将 系统地研究sPLA2活性和脂类特异性T细胞群激活之间的联系，以及 人类CD1限制性T细胞群对磷脂A2来源的磷脂破坏的反应特征 产品。使用T细胞培养和人类皮肤外植体模型，我们将确定PLA2活性是否诱导 激活/扩增溶血磷脂反应性T细胞群。我们将调查人类的广度 溶血磷脂特异性T细胞谱系及其特异性/混杂。为此，我们使用一个面板 溶血磷脂负载CD1四聚体和CD1平板法。最后，我们将应用组合式单电池TCR 正常人和银屑病患者CD1-LPC四聚体T细胞的序列测定和功能表型分析 患者，以确定这些人群主要具有促炎或免疫调节功能，以及 克隆性扩张是否发生在炎症性皮肤病的背景下。这项建议将提供见解 是否sPLA2活性是人类CD1限制性T细胞激活的重要驱动因素，并将阐明 应答T细胞群的特异性和功能。因为sPLA2的活性是急性和慢性疾病的中心 和慢性炎症，这项研究的结果将有助于更好地理解一种常见的生理学 T细胞可以在多种不同的炎症条件下被激活的途径，并提供了新的 对脂类特异性T细胞激活可能在治疗上进行调节的模式的见解。

PROJECT SUMMARY CD1 proteins are structurally related to MHC class I, but instead of peptides, they present lipid antigens to T cells. We and others have shown that CD1-restricted T cells recognizing self-lipids are abundant in the human T cell repertoire, yet it remains unclear how the activation of these T cells is regulated in vivo. Overt reactivity to self-lipids suggests that antigenic CD1-lipid complexes must be tightly regulated in order to prevent continuous T cell stimulation. Both fatty acids and lysophosphatidylcholine (LPC) have been identified as antigens for certain human CD1-restricted T cells. These lipids are released when the enzyme phospholipase A2 (PLA2) acts on membrane phospholipids, supporting a role for PLA2 activity in the generation of CD1 self antigens. Since secreted PLA2 (sPLA2) is increased in response to tissue damage and infections, we hypothesize that sPLA2 activity in humans is a common mechanism through which the activation of CD1-restricted T cells is regulated, by temporarily increasing the availability of CD1 self-lipid antigens. This is supported by our preliminary observations that PLA2 activity on antigen presenting cells results in CD1-dependent T cell activation in healthy individuals. Furthermore, since sPLA2 levels are constitutively elevated in many chronic inflammatory conditions, including rheumatoid arthritis, asthma, atherosclerosis and psoriasis, this mechanism may underlie persistent T cell activation in these conditions through continued high levels of self lipid antigens. In this proposal we will systematically investigate the link between sPLA2 activity and activation of lipid-specific T cell populations, and characterize the human CD1-restricted T cell populations that respond to PLA2-derived phospholipid breakdown products. Using T cell cultures and a human skin explant model, we will determine if PLA2 activity induces the activation/expansion of lysophospholipid-reactive T cell populations. We will investigate the breadth of the human lysophospholipid-specific T cell repertoire, and its specificity/promiscuity. For this we use a panel of lysophospholipid-loaded CD1 tetramers, and a CD1 plate assay. Last, we will apply combined single cell TCR sequencing and functional phenotyping to CD1-LPC tetramer+ T cells isolated from healthy donors and psoriasis patients, to determine if these populations primarily have pro-inflammatory or immunoregulatory functions, and whether clonal expansions occur in the context of inflammatory skin disease. This proposal will provide insight in whether sPLA2 activity is a significant driver of human CD1-restricted T cell activation, and will elucidate the specificities and functions of the responding T cell populations. Because sPLA2 activity is central to both acute and chronic inflammation, results from this study will lead to a better understanding of a common physiological pathway through which T cells can be activated in multiple distinct inflammatory conditions, and provide novel insights in modes through which lipid-specific T cell activation may be regulated therapeutically.