T Cell Immunity in Giant Cell Arteritis

项目摘要 巨细胞动脉炎（GCA）是一种威胁视力的血管炎，由于血管闭塞导致眼部缺血， 供应视神经、视网膜、虹膜或其他眼眶结构的关键动脉。典型的介绍 GCA视力丧失的主要原因是动脉炎性前部缺血性视神经病变（AION）或视网膜中央动脉阻塞， 有很高的发展到第二只眼的风险。失明是可以预防的，如果疾病得到诊断， 及时治疗。GCA患者具有高反应性CD 4 T细胞，其侵入动脉壁层 其中它们与巨噬细胞一起诱导管腔闭塞性内膜增生。驱动CD 4 T的缺陷 细胞高反应性还不清楚。本申请将检验CD 4 T细胞 不能激活免疫保护性程序性细胞死亡蛋白1（PD-1） 检查站在结合其配体程序性死亡配体1（PD-L1）后，PD-1受体传递STOP信号。 信号以抑制T细胞效应子功能。初步研究表明， 来自GCA的树突状细胞（DC）和内皮细胞（EC）上PD-L1免疫抑制配体的表达 患者此外，在携带人动脉和GCA的嵌合小鼠中阻断PD-1免疫检查点， CD 4 T细胞导致血管炎的显著恶化，诱导内皮-间充质转化， 抑制内膜层生长。本提案中设计的实验依赖于一系列使能 资源，特别是对一个大的GCA患者队列，一个GCA影响的颞动脉的生物库和一个 嵌合体系统，其中在移植到免疫缺陷小鼠的人动脉中诱导血管炎。 具体目标1在机制水平上检查PD-L1低树突状细胞如何影响持续时间， 血管生成免疫应答的幅度和质量。实验的目的是 了解PD-L1表达不足如何调节T细胞活化，扩增，组织侵袭， 存活和细胞因子产生。特定目的2研究了PD-L1在外膜上的表达 微血管内皮细胞（MVEC）可以保护血管壁免受免疫攻击， 屏障功能在体外和体内，我们将定义MVEC衍生的负信号如何调节行为， PD-1+ CD 4 T细胞和效应子功能以及内皮PD-L1缺陷如何促进血管生成性T细胞 细胞具体目标3将确定导致GCA DC上PD-L1表达不足的机制， 目的是修复有缺陷的免疫检查点。通过筛选GCA和对照DC对 刺激和信号通路抑制剂，我们已经发现IFN-γ-BMP 4-pSMAD 1/5-IRF 1模块作为一个信号通路抑制剂。 PD-L1表达的关键调节因子。患者来源的DC显示IFN-γ γ不敏感性并且不能上调 典型骨形态发生蛋白（BMP 4）信号传导。我们将探索BMP 4的功能- pSMAD 1/5-IRF 1信号传导轴，并使用ATAC进行表观遗传学研究， 测序以确定差异染色质可及性和调节转录因子网络的区域。

Project Summary Giant cell arteritis (GCA) is a vision-threatening vasculitis that causes ocular ischemia due to occlusion of critical arteries supplying the optic nerve, the retina, the iris, or other orbital structures. The typical presentation of vision loss in GCA is arteritic anterior ischemic optic neuropathy (AION) or central retinal artery occlusion, with a high risk for progression to the second eye. Blindness is preventable if the disease is diagnosed and treated promptly. GCA patients have hyperreactive CD4 T cells that invade into the wall layers of arteries where together with macrophages they induce lumen-occlusive intimal hyperplasia. The defect driving CD4 T cell hyperreactivity is not understood. The current application will examine the hypothesis that CD4 T cells from GCA patients fail to activate the immuno-protective Programmed cell death protein 1 (PD-1) checkpoint. Upon binding its ligand Programmed death-ligand 1 (PD-L1), the PD-1 receptor transmits a STOP signal to inhibit T cell effector functions. The proposal builds on preliminary studies demonstrating low expression of the PD-L1 immuno-inhibitory ligand on dendritic cells (DC) and endothelial cells (EC) from GCA patients. Also, blockade of the PD-1 immune checkpoint in chimeric mice carrying human arteries and GCA CD4 T cells results in marked exacerbation of vasculitis, induces endothelial-mesenchymal transition and aggravates intimal layer outgrowth. Experiments designed in this proposal rely on a series of enabling resources, specifically on a large cohort of GCA patients, a biobank of GCA-affected temporal arteries and a chimera system in which vasculitis is induced in human arteries engrafted into immune-deficient mice. Specific Aim 1 examines on a mechanistic level how PD-L1low dendritic cells affect the duration, the amplitude and the quality of vasculitogenic immune responses. Experiments have been designed to understand how insufficient expression of PD-L1 modulates T cell activation, expansion, tissue invasion, survival and cytokine production. Specific Aim 2 investigates how PD-L1 expression on adventitial microvascular endothelial cells (MVEC) shields the vessel wall from immune attack and protects vascular barrier function. In vitro and in vivo, we will define how MVEC-derived negative signals modulate the behavior and effector functions of PD-1+ CD4 T cells and how endothelial PD-L1 deficiency promotes vasculitogenic T cells. Specific Aim 3 will identify mechanisms leading to insufficient PD-L1 expression on GCA DC, with the goal to repair the defective immune checkpoint. By screening the responsiveness of GCA and control DC to stimuli and signaling pathway inhibitors, we have discovered the IFN-γ-BMP4-pSMAD1/5-IRF1 module as a critical regulator of PD-L1 expression. Patient-derived DC display IFN-γinsensitivity and fail to upregulate canonical bone morphogenetic protein (BMP4) signaling. We will probe the functionality of the BMP4- pSMAD1/5-IRF1 signaling axis and complement these experiments with epigenetic studies using ATAC sequencing to define regions of differential chromatin accessibility and regulatory transcription factor networks.