The role of cross-presentation of self-antigens by dendritic cells in type 1 diabetes

 描述(申请人提供)：1型糖尿病(T1D)是一种自身免疫性疾病，影响300多万美国人。其特点是CD4+和CD8+T细胞对胰岛中的β细胞的侵袭和破坏。我们实验室最近的工作也证明了CD8CD8+α+树突状细胞在T1D的启动中是必不可少的。 这些细胞通常负责细胞外抗原的交叉提呈，以激活细胞毒性T细胞对细胞内病原体的反应。然而，CD8CD8+α+树突状细胞也可能不适当地交叉呈现自身抗原，例如来自胰腺β细胞的自身抗原，以启动针对正常宿主组织的CD8+T细胞反应。这种无意的功能可能解释了为什么它们是启动T1D所必需的。因此，确定交叉呈现的机制及其在自身免疫中的作用可能会为T1D的发病机制提供重要线索，也可能加速预防其发病的治疗措施的发展。在这项提案中，我们将确定交叉呈现发生的机制以及它在T1D中所起的作用。为了研究这些问题，我们创造了新的Rab43基因敲除小鼠。这些小鼠的CD8CD8α+树突状细胞在体内和体外均表现出缺乏的交叉呈递。在目标1中，我们将确定Rab43将抗原定向到细胞内的囊泡通路以进行交叉呈递。我们还将确定哪些细胞外受体将Rab43招募到吞噬体以交叉呈现其内容。在目标2中，我们将确定不足的交叉呈现是否影响T1D的发展。我们将使用非肥胖糖尿病(NOD)小鼠品系作为T1D的模型，因为它概括了人类疾病的许多特征，包括胰岛β细胞的自发破坏。我们将Rab43基因敲除的等位基因回交到NOD背景上，以产生NOD.Rab43-/-菌株，该菌株将在糖尿病易感性背景上表现出不足的交叉呈现。我们将确定这些小鼠是否对高血糖和胰岛β细胞的破坏具有抵抗力。我们将进一步分析该菌株在激活介导β细胞破坏的自身反应性CD8+T细胞方面是否存在选择性缺陷。综上所述，这一提议产生的发现应该确定交叉呈现是否在T1D的发病机制中发挥作用，如果是的话，也将确定其治疗调节可以阻止自身免疫反应的启动的途径。

 DESCRIPTION (provided by applicant): Type 1 diabetes (T1D) is an autoimmune disease that affects more than 3 million Americans. It is characterized by the infiltration and destruction of beta cells in the pancreatic islets of Langerhans by CD4+ and CD8+ T cells. Recent work from our labs has also demonstrated that CD8α+ dendritic cells are essential for the initiation of T1D. These cells are normally responsible for cross-presentation of extracellular antigens in order to activate a cytotoxic T cell response against intracellular pathogens. CD8α+ dendritic cells may, however, also inappropriately cross-present self-antigens, such as from pancreatic beta cells, in order to initiate a CD8+ T cell response against normal host tissues. This inadvertent function may explain why they are necessary for the initiation of T1D. Determining the mechanisms of cross-presentation and its role in autoimmunity may therefore provide vital clues into the pathogenesis of T1D, and may also hasten the development of therapeutic measures to prevent its onset. In this proposal, we will identify the mechanisms by which cross-presentation occurs and the role it plays in T1D. In order to investigate these questions, we have generated novel Rab43 knockout mice. CD8α+ dendritic cells from these mice exhibit deficient in vitro and in vivo cross-presentation. In Aim 1, we will identify the intracellular vesicular pathways to which Rab43 directs antigen for cross-presentation. We will also determine what extracellular receptors recruit Rab43 to phagosomes in order to cross-present their contents. In Aim 2, we will determine whether deficient cross-presentation impacts the development of T1D. We will use the non-obese diabetic (NOD) mouse strain as a model of T1D, as it recapitulates many features of the human disease including the spontaneous destruction of islet beta cells. We will backcross the Rab43 knockout allele onto the NOD background in order to produce the NOD.Rab43-/- strain, which will exhibit deficient cross- presentation on a background of susceptibility to diabetes. We will characterize whether these mice are resistant to the development of hyperglycemia and the destruction of islet beta cells. We will further analyze whether this strain has a selective deficiency in activating the autoreactive CD8+ T cells that mediate the destruction of beta cells. Together, the findings generated from this proposal should determine whether cross- presentation plays a role in the pathogenesis of T1D, and, if so, will also identify the pathways whose therapeutic modulation could prevent the initiation of the autoimmune response.