Tissue Cytokine Sequestration and Immune Regulation in Autoimmunity

项目摘要/摘要 在健康个体中，免疫反应部分由Foxp3调节性T细胞(Treg)解决。在……里面 患有1型糖尿病(T1D)或多发性硬化症(MS)的人，Treg在体外功能良好，但无法 预防疾病。这意味着自身免疫中Treg功能的体内损害。 控制Treg动态平衡的关键因素是细胞因子白介素2(IL-2)。与某些细胞因子不同， 在自由循环的情况下，IL-2主要与细胞外基质结合，特别是与硫酸肝素(HS)结合。 我们已经确定了迄今为止被忽视的HS介导的IL-2在Treg功能中的基础作用 和体内的稳定性。众所周知，含有HS的蛋白多糖(HSPGs)可以保留并缓慢释放 随着时间的推移，其他细胞因子和生长因子，从而促进损伤后的组织重塑。我们发现 这种炎症增加了组织保留IL-2的能力。我们还发现HS结合的IL-2(HS/IL-2) 作为IL-2R信号的超级激动剂，促进Treg的扩张和稳定。最后，我们发现 乙酰肝素酶(HPSE)和HS分解代谢是Treg在体外和体内发挥作用所必需的，这表明 Treg可以使用HPSE从细胞外基质中的HSPG中剥离IL-2。 相反，在自身免疫中，HS/IL-2的隔离和获取可能受到损害。Hs有丰富的 健康的胰岛，但在自身免疫性岛炎的背景下消失。同样，HSPG的模式是 MS的白质病变内精神错乱。 从治疗的角度重述HS/IL-2信号是可能的。利用耐受性 在HS/IL-2的基础上，我们开发了HS/IL-2的合成模拟物，对Treg进行了扩展。我们的愿景是，这些可以 与抗原结合，用于诱导Treg和预防MS和T1D。 根据这些令人兴奋的初步数据，我们假设HS/IL-2促进Treg功能，并且这 自身免疫途径受损。我们将在实验中验证这一假设，目的如下： 在目标1中，我们将评估T1D和MS中细胞因子的ECM结合。 在目标2中，我们将阐明HS/IL-2如何作为IL-2R信号的超级激动剂。 在目标3中，我们将开发HS/IL-2复合体，以促进Treg诱导和免疫耐受。 这些目标加在一起有可能改变我们对促进 外周组织的免疫动态平衡。

Project Summary/Abstract In healthy individuals, immune responses are resolved in part by Foxp3+ regulatory T-cells (Treg). In individuals afflicted with type 1 diabetes (T1D) or Multiple Sclerosis (MS), Treg function well ex vivo but fail to prevent disease. This implicates in vivo impairments in Treg function in autoimmunity. A critical factor that governs Treg homeostasis is the cytokine interleukin 2 (IL-2). Unlike some cytokines that circulate freely, IL-2 is mostly bound to the ECM, specifically to heparan sulfate (HS). We have identified a heretofore ignored, fundamental role for HS-mediated IL-2 sequestration in Treg function and stability in vivo. It is well-established that HS-containing proteoglycans (HSPGs) retain and slowly release other cytokines and growth factors over time, thereby contributing to tissue remodeling after injury. We find that inflammation increases the ability of tissues to retain IL-2. We also find that HS-bound IL-2 (HS/IL-2) functions as a superagonist of IL-2R signaling, promoting the expansion and stability of Treg. Finally, we find that heparanase (HPSE) and HS catabolism are required for Treg function in vitro and in vivo, suggesting that Treg may use HPSE to strip IL-2 from HSPG within the extracellular matrix. Conversely, HS/ IL-2 sequestration and acquisition may be impaired in autoimmunity. HS is abundant in healthy pancreatic islets but disappears in the setting of autoimmune insulitis. Similarly, patterns of HSPGs are deranged within white matter lesions in MS. It may be possible to recapitulate HS/IL-2 signals therapeutically. Capitalizing on the tolerogenic properties of HS/IL-2, we have developed synthetic mimetics of HS/IL-2 that expand Treg. Our vision is that these can be conjugated to antigens and used to induce Treg and prevent MS and T1D. In light of these exciting preliminary data, we hypothesize that HS/ IL-2 promotes Treg function and that this pathway is impaired in autoimmunity. We will test this hypothesis in experiments with the following aims: In Aim 1 we will evaluate ECM binding of cytokines in T1D and MS. In Aim 2 we will elucidate how HS/IL-2 acts as a superagonist of IL-2R signaling. In Aim 3 we will develop HS/IL-2 complexes that promote Treg induction and immune tolerance. Together these Aims have the potential to transform our understanding of the mechanisms that promote immune homeostasis in peripheral tissues.