VASCULOPATHY, APOPTOSIS AND AUTOIMMUNITY

该建议的重点是血管病变导致系统性硬化症的纤维化和自身免疫表现的分子机制。 由系统性硬化症患者产生的自身抗体独特地靶向核仁蛋白，如DNA拓扑异构酶I（topo-I）。 已经证明，拓扑-I是对凋亡过程特异的蛋白酶的底物，产生新的切割片段，其可以揭示宿主先前未耐受的隐蔽表位。 最近还证实，在弥漫性硬皮病中靶向的几种自身抗原独特地易受金属催化氧化反应的裂解，类似于在适当金属存在下缺血再灌注期间可能发生的反应。 这一过程也可能揭示免疫密码表位，并为为什么某些蛋白质是系统性硬化症免疫应答的独特靶点提供分子解释。 然而，众所周知，单独的隐蔽表位不足以产生自身反应性，这还需要分子佐剂的参与，以及具有共刺激能力的抗原呈递细胞（APC）对潜在自身抗原的摄取。 该建议的中心假设是，系统性硬化症患者的慢性缺血-再灌注损伤不仅在皮肤来源的核仁自身抗原内产生免疫密合表位，而且还产生补体配体，其提供打破免疫耐受所需的分子佐剂。 该提议的具体目的是：1）确定携带补体配体的凋亡性大泡调节抗原呈递细胞的细胞因子表达和共刺激能力的能力，2）表征对含自身抗原的凋亡性大泡的免疫应答，和3）检测补体配体C3 d在体外诱导对topo I的自身反应性T和B细胞应答过程中的作用. 虽然系统性硬化症是这项建议的重点，这些研究产生的数据应该提供深入了解我们的血管病变和自身免疫过程的一般。

This proposal is focused upon the molecular mechanism by which vasculopathy leads to fibrotic and autoimmune manifestations of systemic sclerosis. Autoantibodies generated by patients with systemic sclerosis are uniquely targeted to nucleolar proteins such as DNA topoisomerase I (topo-I). It has been demonstrated that topo-I is a substrate for protease(s) specific to the apoptotic process, resulting in novel cleavage fragments that may reveal cryptic epitopes to which the host has not previously been tolerized. It has also been recently demonstrated that several of the autoantigens targeted in diffuse scleroderma are uniquely susceptible to cleavage by metal-catalyzed oxidation reactions similar to what may occur during ischemia-reperfusion in the presence of appropriate metals. This process may also reveal immunocryptic epitopes and provides a molecular explanation for why certain proteins are uniquely targeted by the immune response in systemic sclerosis. However, it is well known that a cryptic epitope alone is not sufficient to generate autoreactivity, which also requires the participation of a molecular adjuvant, and uptake of the potential autoantigen by an antigen presenting cell (APC) with costimulatory capacity. The central hypothesis of this proposal is that chronic ischemia-reperfusion injury in patients with systemic sclerosis not only generates immunocryptic epitopes within nucleolar autoantigens of cutaneous origin, but it also generates complement ligands that provide the molecular adjuvant required to break immune tolerance. The specific aims of this proposal are to: 1) Determine the capacity of apoptotic blebs bearing complement ligands to modulate the cytokine expression and costimulatory capacity of antigen presenting cells, 2) characterize the immune responses to self antigen- containing apoptotic blebs, and 3) examine the role of complement ligand C3d during induction of autoreactive T and B cell responses to topo I in vitro. Although systemic sclerosis is the focus of this proposal, the data generated by these studies should provide insight into our understanding of vasculopathic and autoimmune processes in general.