Immunological Mechanisms Underlying T1dm Pathogenesis

1型糖尿病(T1 DM)是一种自身免疫性疾病，由位于胰腺的T细胞介导的产生胰岛素的β细胞破坏引起。目前的治疗方法包括注射胰岛素替代、频繁的血糖监测和饮食/锻炼纪律，可以防止因激素不足而死亡，但不能治愈，也无法防止长期并发症。这些并发症包括神经损伤和血管恶化(大血管和小血管)，导致各种器官受损，包括心脏、脑、肾脏和眼睛。与类似的人相比，预期寿命缩短了三分之一，但没有T1 DM。这项工作始于20世纪90年代中期海军医学研究所的S，在德国乌尔姆大学进一步发展，随后在NIDDK-TAB工作了一年，利用大鼠胰岛素启动子-CD80转基因小鼠(RIP-CD80小鼠)建立了一种独特的自身免疫性糖尿病小鼠模型。这些动物基于其共刺激分子CD80的β细胞特异性表达，容易受到免疫介导的β细胞破坏。虽然RIP-CD80小鼠很少发生自发性糖尿病(发病率6.7%，与野生型小鼠相比)，但我们观察到并初步表征了这些小鼠在β细胞自身抗原(即这些小鼠的胰腺β细胞特异性表达的蛋白质分子)免疫后表现出的进行性胰岛浸润并最终发展为胰岛素依赖型糖尿病(IDDM)的深刻敏感性。例如，与非转基因小鼠不同，这些动物在胰岛素前体免疫后统一发展为胰岛细胞破坏和IDDM，胰岛素前体是一种强烈怀疑与人类T1 DM发病有关的β细胞自身抗原。我们已经证明，成熟的胰岛素分子中必须至少存在一个相关的自身抗原性CTL表位(H-2b)，这与目前基于算法节律的表位预测模型形成了对比。此外，到目前为止，我们的模型被证明是令人惊讶的预测，并且对非肥胖糖尿病(NOD)小鼠的反应要准确得多，非肥胖糖尿病(NOD)小鼠是研究自身免疫性糖尿病最广泛使用的模型。本实验室使用上述小鼠模型的目的可概括如下：(1)我们正在准备鉴定自身抗原及其CTL表位，它们被认为是发展自身免疫反应的重要初始靶标抗原。为此，我们将探索几种候选自身抗原的免疫途径，包括多肽免疫、DNA疫苗和逆转录病毒转导的树突状细胞(DC)，以了解它们在RIP-CD80转基因小鼠中诱导(MHC I类限制)T细胞反应、胰岛素炎和糖尿病的能力。(2)我们将研究过继转移模型中的β细胞特异性T细胞反应，其中自身反应性T细胞的初级致敏将发生在体外或通过体内免疫，如(1)所建议的。这些研究将集中于1)和2)中所述的发展中的β细胞破坏性免疫反应的机制，并将试图找出干扰正在进行的免疫反应的新的治疗方法。最后，(3)我们将继续探索我们的初步数据，表明非专业抗原呈递的MG细胞(APC)，如胰腺β细胞或成纤维细胞，可以在体内启动幼稚的前体CTL，并刺激相当慢性的自身免疫反应。相比之下，专业的APC来自于DC等造血系，会导致相当均匀和猛烈的胰岛破坏和糖尿病，这在人类疾病中是不常见的。

Type 1 Diabetes Mellitus (T1DM) is an autoimmune disease resulting from the T cell mediated destruction of insulin-producing beta cells located in the pancreas. Current treatment, which includes insulin replacement by injection, frequent blood glucose monitoring, and dietary/exercise discipline, can prevent death from hormonal insufficiency, but is not curative and does not prevent long-term complications. Those complications include nerve damage and vascular deterioration (large and small blood vessels) resulting in damage to various organs, including the heart, brain, kidneys, and eyes. Life expectancy is shortened by an estimated one-third compared to similar individuals but without T1DM. This work, initiated in the mid 1990's at the Naval Medical Research Institute and further developed at the University of Ulm in Germany and subsequently for the past year at the NIDDK-TAB, has characterized a unique murine model of autoimmune diabetes using rat-insulin promoter (RIP)-CD80 transgenic mice (RIP-CD80 mice). These animals are predisposed to immune mediated beta cell destruction based on their beta cell-specific expression of the costimulatory molecule CD80. While RIP-CD80 mice rarely develop spontaneous diabetes (incidence 6.7%, compared to none of wild type mice), we have observed and have initially characterized the profound susceptibility these mice display to develop progressive islet infiltration and eventually insulin dependent diabetes mellitus (IDDM) following immunization with beta cell autoantigens (i.e. protein molecules that are expressed specifically by the pancreatic beta cells of these mice). For instance, these animals, unlike non-transgenic littermates, uniformly develop islet cell destruction and IDDM upon immunization with insulin precursors, a beta cell autoantigen strongly suspected to be involved in the pathogenesis of T1DM in humans. We have shown that at least one relevant autoantigenic CTL epitope (H-2b) must be present in the mature insulin molecule, which contrast with current algorhythm-based epitope prediction models. Moreover, our model turned out to be so far amazingly predictive and much more accurate of reponses by the non-obese diabetic (NOD) mouse, a model most widely used to study autoimmune diabetes. This laboratory's objective using the above mouse model can be summarized as follows:(1) We are preparing to identify self-antigens (Ag) and CTL-epitopes thereof that are thought to be important initial target Ag for the developing autoimmune response. For this purpose, we will explore several routes of immunization of candidate auto-antigens, including peptide immunizations, DNA-vaccines, and retrovirally transduced dendritic cells (DC), for their ability to elicit (MHC class I restricted) T cell responses, insulitis, and diabetes in RIP-CD80 transgenic mice.(2) We will study beta cell specific T cell responses in an adoptive transfer model where the primary sensitization of the autoreactive T cells will take place either in vitro, or by immunizing in vivo, as proposed in (1). These studies will focus on the mechanisms of the developing beta cell destructive immune responses, as described in 1) and 2), and will attempt to identify novel therapeutic approaches to interfere with the ongoing immune responses. Finally, (3) we will continue to explore our preliminary data suggesting that non-professional antigen-presentinmg cells (APC), such pancreatic beta cells or fibroblastoid cells, can prime naive precursor CTL in vivo, and stimulate a rather chronic autoimmune response. In contrast, professional APC, derived from the haematopoetic lineage such as DC, induce a rather uniform and fulminant islet destruction and diabetes, not typically seen in human disease.