Exosome-induced innate and antigen-specific immune responses in Type 1 Diabetes

描述（由申请人提供）：1型糖尿病（T1D）是一种T细胞介导的组织特异性自身免疫性疾病，其中II类MHC基因在控制疾病易感性方面起主要作用。这表明，胰岛自身抗原及其在MHC分子上呈现的短肽是导致胰岛中产生胰岛素的β细胞被破坏的关键因素。由于胸腺的自我耐受机制通常能有效清除强自身反应性T细胞，因此清除外周循环T细胞以避免自身反应性；然而，尽管发病率很低，自身免疫性疾病也会发生。我们假设某些炎症触发因素可能通过增强胰岛自身抗原的免疫原性活性来启动胰岛的自身免疫反应。我们对一种候选胰岛抗原谷氨酸脱羧酶65 KDa （GAD65）进行了数年的研究，并了解到诱导致病或致糖尿病效应T细胞需要独特的抗原递送和加工途径，并证明糖尿病相关的候选基因Slc11a1可以改变树突状细胞（DC）中胰岛抗原的加工途径。我们最近从小鼠胰岛素瘤和原代胰岛胶质细胞培养上清中分离出一种微颗粒/囊泡，即外泌体（EXO），发现EXO含有强促炎物质，可刺激包括DC在内的各种抗原呈递细胞产生炎症细胞因子，上调MHC和共刺激分子；更重要的是，从原代胰岛胶质细胞中收集的EXO也表达了几种已知的胰岛自身抗原，包括GAD65。因此，我们提出了一个新的假设，即EXO可能作为一种独特的内源性佐剂和抗原载体，可以调节APC改变自身抗原的加工/呈递，从而激活自身反应性T细胞。在本研究中，我们将首先对原代胰岛细胞释放的EXO进行基本的生物化学分析，并研究不同tlr在EXO诱导的先天反应中的需求，以表征EXO中包含的促炎物质的性质。我们将比较糖尿病易感NOD菌株和耐药NOD菌株之间的胰岛胶质细胞及其EXO，以确定异常或过量的EXO产生是否可能是糖尿病的一个致病事件。然后，我们将使用EXO作为抗原载体，研究在DC中处理EXO后如何诱导针对胰岛抗原（特别是GAD65）的自身反应效应T细胞。我们预测，在应激或炎症情况下，通过EXO分泌增加的胰岛抗原泄漏是激活高致糖尿病性T细胞的关键。最后，我们将继续研究Slc11a1基因在DC活化和抗原加工中的作用。我们将使用EXO作为激活DC和传递抗原的载体。我们预计EXO可以上调Slc11a1在DC中的功能，从而促进致病Th1细胞的诱导。

DESCRIPTION (provided by applicant): Type 1 diabetes (T1D) is a T cell-mediated, tissue-specific autoimmune disease, in which the class II MHC genes play a major role controlling the disease susceptibility. This suggests that islet autoantigens and their short peptides presented on the MHC molecules are the key elements leading to the destruction of the insulin-producing beta cells in the pancreatic islets. Since self-tolerance mechanism in the thymus normally is effective in removing strong autoreactive T cells, peripheral circulating T cells are purged to avoid self- reactivity; however, autoimmune disease does occur despite of rare incidence. We hypothesized that certain inflammatory triggers may initiate the autoimmune responses in the islets by enhancing the immunogenic activity of the islet autoantigens. We have studied one candidate islet antigen, glutamic acid decarboxylase 65 KDa (GAD65), for several years and learned that unique antigen delivery and processing pathways are required to induce disease-causing or diabetogenic effector T cells, and demonstrated that a diabetes- associated candidate gene, Slc11a1, could alter the pathways of processing islet antigens in dendritic cells (DC). We recently isolated one type of microparticles/vesicles, namely exosomes (EXO), from the culture supernatants of mouse insulinomas and primary islet glial cells, and found that the EXO contains strong proinflammatory materials that could stimulate various antigen presenting cells including DC to produce inflammatory cytokines and upregulate MHC and costimulatory molecules; more importantly, the EXO collected from the primary islet glial cells also expresses several known islet autoantigens including GAD65. We thus propose a novel hypothesis that EXO may act as a unique type of endogenous adjuvant and antigen carrier that can condition APC to alter the processing/presenting of the autoantigens and thus, to activate the autoreactive T cells. In this proposal, we will first perform basic biochemistry analysis for the EXO released by the primary islet cells, and study the requirements of different TLRs in the EXO-induced innate responses to characterize the nature of the proinflammatory materials enclosed in the EXO. We will compare the islet glial cells and their EXO between diabetes-susceptible NOD strain and resistant strains to address whether abnormal or excess EXO production could be one diabetes-causative event. Then, we will use EXO as an antigen carrier to study how autoreactive effector T cells specific for islet antigens, particularly GAD65, are induced following processing the EXO in DC. We predict that increased leakage of islet antigens via EXO secretion under stress or inflammatory situation is the key for activating highly diabetogenic T cells. Finally, we will continue studying the Slc11a1 gene for its roles in DC activation and antigen processing. We will use EXO as a vehicle for activating DC and delivering antigens. We anticipate that EXO can upregulate Slc11a1 function in DC and thus promote induction of the disease-causing Th1 cells.