Effects of aging on immunity and autoimmunity

描述(申请人提供)：重症肌无力(MG)是一种进行性自身免疫性疾病，患者会出现严重的肌肉无力，并随着疲劳而恶化。这些症状是由于针对位于神经肌肉接头的乙酰胆碱受体(AChR)的自身抗体。对于许多MG患者(40%-60%)来说，疾病发生在40岁之后。此外，在超过70%的MG患者中发现胸腺细胞异常和/或胸腺瘤(肿瘤)，这表明胸腺也在疾病进展中发挥作用。由于胸腺是T细胞成熟的部位，负责清除“自身”反应性T细胞，因此MG的发生可能是由于胸腺在维持免疫耐受方面的缺陷。鉴于胸腺随着年龄的增长而退化，我们推测，与胸腺控制丧失相关的免疫失调可能在晚发性MG和其他老年人自身免疫性疾病中发挥作用。目前的应用主要集中在评估为什么免疫和自身免疫会受到年龄的不同影响，确定胸腺在建立和维持对自身AChR的耐受中的作用，以及在一种新的迟发性MG模型中测试潜在的治疗靶点。Aim I的实验将集中在MG小鼠模型中对自身决定簇和外源决定簇的抗体反应。使用以前从用加州鱼雷的乙酰胆碱受体免疫的小鼠收集的血清，ELISA将被用来评估识别“自我”的抗体效价，小鼠AChR，相对于外来蛋白，鱼雷AChR的反应。在AIM II中，我们将直接询问胸腺是否需要产生对AChR的耐受。将在裸鼠(无胸腺)身上进行胸腺移植，以产生只在胸腺、肌肉、两种组织或两者都不表达TAChR转基因的动物。这些嵌合动物将被免疫，并将测量T细胞耐受性水平(缺乏增殖)。我们还将关注自身免疫调节因子AIRE，这是一种控制胸腺外周抗原表达的转录因子。我们将确定AIRE是否参与AChR的调节，如果是，AIRE基因敲除的小鼠是否更容易患上自身免疫性MG。AIM III的设计目的是在我们新的迟发性MG模型中测试以前在年轻小鼠身上探索的治疗方法。我们将第一次能够问，针对MG的免疫疗法是否对老年人有效。总之，我们在阐明衰老对MG自身抗原AChR耐受性和免疫力的影响方面是独一无二的。拟议的研究结果可能为其他起病较晚的自身免疫性疾病提供新的见解，包括干燥综合征、特发性炎症性肌病和恶性贫血。利用新的TAChR转基因小鼠模型和第一个迟发性重症肌无力(MG)模型，我们的实验室在阐明衰老对MG自身抗原AChR耐受和免疫的影响方面具有独特的地位。 拟议的研究结果可能为其他起病较晚的自身免疫性疾病提供新的见解，包括干燥综合征、特发性炎症性肌病和恶性贫血。了解对自身蛋白的耐受机制以及胸腺退化和/或年龄相关的免疫失调对这些过程的破坏是开发新的治疗方法的关键第一步。

DESCRIPTION (provided by applicant): Myasthenia gravis (MG) is a progressive autoimmune disorder in which patients develop severe muscle weakness which worsens with fatigue. The symptoms are due to autoantibodies directed against acetylcholine receptors (AChR) located at the neuromuscular junctions. For many MG patients (40-60%), disease onset occurs after the age of 40. In addition, thymus cellular abnormalities and/or thymomas (tumors) are found in more than 70% of MG patients, suggesting that the thymus plays a role in disease progression as well. Since the thymus is the site of T cell maturation and is responsible for eliminating 'self' reactive T cells, it is possible that MG arises due to thymic deficiencies in maintaining immune tolerance. Given that the thymus involutes with aging, we hypothesize that immune dysregulation associated with the loss of thymic controls may play a role in late onset MG and in other autoimmune disorders in the elderly. The current application is focused on assessing why immunity and autoimmunity are differentially affected by aging, determining the role of the thymus in establishing and maintaining tolerance to self AChR, and testing potential therapeutic targets in a novel late-onset model of MG. Experiments in Aim I will focus on antibody responses to self versus foreign determinants in the murine model of MG. Using previously collected sera from mice immunized with the acetylcholine receptor from Torpedo californica, ELISAs will be used to assess the titers of antibodies that recognize 'self', mouse AChR, relative to reactivities to the foreign protein, Torpedo AChR. In Aim II, we will ask directly whether the thymus is required for generating tolerance to AChR. Thymic grafts will be performed onto nude (athymic) mice in order to generate animals which express the TAChR transgene only in thymus, only in muscle, in both tissues, or in neither. These chimeric animals will be immunized and the level of T cell tolerance (lack of proliferation) will be measured. We will also focus on AIRE, the autoimmune regulator, a transcription factor that controls expression of peripheral antigens in the thymus. We will determine whether AIRE is involved in the regulation of AChR, and if so, whether AIRE knock-out mice are more susceptible to autoimmune MG. Aim III is designed to test therapeutic approaches previously explored in young mice in our novel late onset MG model. We will be able to ask, for the first time, whether immunotherapies for MG will be effective in older individuals. In summary, we are uniquely positioned to elucidate the effects of aging on tolerance and immunity to AChR, the autoantigen in MG. The results of the proposed studies may provide novel insights into other autoimmune disorders with late onset disease etiologies, including Sjogren syndrome, idiopathic inflammatory myopathy, and pernicious anemia. Using both the novel TAChR transgenic mouse model and the first model of late-onset Myasthenia gravis (MG), our laboratory is uniquely positioned to elucidate the effects of aging on tolerance and immunity to AChR, the autoantigen in MG. The results of the proposed studies may provide novel insights into other autoimmune disorders with late onset disease etiologies, including Sjogren syndrome, idiopathic inflammatory myopathy, and pernicious anemia. Understanding the mechanisms of tolerance to self proteins and the disruption of these processes by thymic involution and/or age-associated immune dysregulation is a crical first step in developing novel therapeutic approaches.