模拟胰岛“hybrid”修饰抗原诱导tolDC免疫保护1型糖尿病β细胞研究

Protection of the islet β cells from autoimmune destruction is important in prevention of type 1 diabetes (T1D). However, the initiate factors and critical antigens of the damage to human islets remain unknown. So far, immune tolerance therapies with single or arbitrary combination of islet antigens/epitopes haven’t achieved satisfactory results. Recent studies have shown that islet-infiltrating T cells recognized to a number of post-translationally modified (PTM) peptides, including hybrid insulin peptide fusions. In previous studies, we have found there were significant individual and time difference in T1D diabetogenic epitopes, and the responses of T cells to islet antigens became stronger after PTM. Heterogeneous protein produced by islet beta cell itself through hybrid and PTM may be the initial factor. “Epitope spreading” leads more pathogenic T cells attacking beta cells, and causes beta cell function failure. So we intend to induce natural specific immune tolerance of islet hybrid mimic antigen by apoptotic beta cells. We will administrate islet specific tolerogenic dendritic cells (tolDC) to NOD-Prkd(cscid)Il2rg(null) mouse to observe the incidence of diabetes and explore the relative mechanisms. We may explore a new strategy of T1D antigen specific immune tolerance therapy through this study.

诱导胰岛抗原特异性免疫耐受是阻止1型糖尿病(T1DM)β细胞损伤的关键，但致人类胰岛免疫损伤的始动因素与关键靶抗原至今未明，以往采用单一或任意组合的胰岛抗原/表位诱导免疫耐受效果不佳。最新研究表明胰岛抗原存在共价交联剪切融合(hybrid)和翻译后修饰(PTM)。申请人前期发现T1DM致病表位存在显著个体和时间差异，并证实PTM能增强致病T细胞对胰岛抗原的靶向攻击。因此β细胞本身出错产生异构蛋白可能是胰岛自身免疫损伤的始动因素；胰岛抗原hybrid修饰将引起自身抗原表位暴露、释放，并致“表位扩展”使β细胞加速衰竭。课题拟利用凋亡β细胞模拟T1DM病理过程天然胰岛抗原修饰组合模式，诱导胰岛“hybrid”修饰抗原特异性免疫耐受，并利用人源化NOD-Prkd(cscid)Il2rg(null)鼠模型探究胰岛抗原tolDC减轻胰岛自身免疫损伤机制，为T1DM抗原特异性免疫耐受治疗探索新的方法。

1型糖尿病（T1DM ）是一种 T细胞介导的以胰岛 β细胞靶向破坏为主要特征的器官特异性自身免疫性疾病，通过特异性胰岛自身抗原诱导免疫耐受，将有望治愈T1DM。本课题针对hybrid insulin peptides（HIPs）---胰岛抗原共价交联剪切融合而成的新表位多肽，以耐受性 DC(tolDCs)为载体，重建抗原特异性免疫耐受来为T1DM免疫治疗探索新的方法。本研究成功诱导培养出低表达共刺激分子，高表达共抑制分子的tolDC，并在体外对其进行了表型鉴定。之后在功能实验中，将加载有HIPs的tolDC与BDC2.5 T细胞共培养，CFSE细胞增殖实验发现T细胞的增殖比例下降，且活化的T细胞比率下降，而Treg亚群比例升高，证明HIPs-tolDC可以通过抑制抗原特异性T细胞的增殖并上调抗原特异性Treg的产生来诱导HIPs抗原特异性免疫耐受。本课题阐述了tolDC在诱导HIPs特异性免疫耐受方面的可能性，为 T1DM的免疫治疗打开了新思路。