Mac-1 (CR3) and Fc gamma receptors in immune-mediated neutrophil cytotoxicity

描述（由申请方提供）：嗜中性粒细胞和巨噬细胞的吞噬功能对于微生物感染的免疫力至关重要，但也可能导致炎症反应和自身免疫性病理过程中的组织损伤。本申请的总体目标是继续扩大我们对吞噬细胞细胞毒性的分子基础的理解，重点是吞噬细胞上的两个主要调理素受体，Fc？Rs（IgG免疫复合物受体）和2整合素Mac-1（补体片段iC 3b受体）。过去4年的主要成就是：1）证明Vav蛋白，Rho GT3家族成员的交换因子是几种Mac-1和Fc？R介导的中性粒细胞粘附功能，2）确定Vav蛋白作为主要的信号转导的NADPH氧化酶激活后，Fc？R参与，通过调节Rac GTP酶和磷酸化的NADPH氧化酶p40 phox，3）目前在体内的证据表明，中性粒细胞Fc？R依赖性而非补体依赖性的组织损伤需要Vav和Rac蛋白，4）通过src和syk激酶的激活，确定Mac-1在体内触发嗜中性粒细胞弹性蛋白酶释放和随后的出血性血管炎中的作用，和5）证明Mac-1在另外两种补体依赖性模型（大疱性类天疱疮和血栓性肾小球肾炎）中对嗜中性粒细胞的关键作用。目前的应用程序建立在这些发现的基础上。目的我是描绘中性粒细胞吞噬机制，补体C3介导的组织损伤和宿主防御有关。特别是，我们将研究导致Mac-1结合其目标和那些连接Mac-1下游效应功能的信号。在目的二，我们将进一步描绘的机制Vav介导的调控NADPH氧化酶后Fc？嗜中性粒细胞和巨噬细胞中的R参与。我们还将阐明Vav和Rac在自身免疫性溶血性贫血模型中IgG或补体介导的巨噬细胞吞噬作用中的作用。我们预计，我们目标的完成应该会让我们更好地了解将调理素受体与特定吞噬细胞细胞毒性功能联系起来的信号通路。这可能有助于设计治疗方法，以选择性靶向负责炎症和自身免疫性疾病中组织损伤的途径，同时最大限度地减少对宿主防御的影响。 公共卫生相关性：本提案的目的是了解介导真皮微血管损伤的中性粒细胞依赖性机制，这是一种公认的导致终末器官/皮肤疾病的自身免疫性损伤靶点。例如，在自身免疫性风湿性疾病中观察到血管壁的炎性破坏，血管炎，其中皮肤受累是最常见的，中性粒细胞积聚是常见特征。干扰中性粒细胞运输的药物如那他珠单抗在自身免疫性疾病中表现出显著的治疗效果，但也表现出潜在的致命性免疫抑制。在本申请中，我们提出描绘可能促进微血管组织损伤但不需要中性粒细胞募集的信号通路。这可能会导致确定有针对性的治疗策略，减轻器官损伤，同时最低限度地免疫妥协的主机。

DESCRIPTION (provided by applicant): Phagocytic functions of neutrophils and macrophages are essential for immunity to microbial infection, but can also contribute to tissue injury during inflammatory responses and autoimmune pathologies. The overall goal of this application is to continue to extend our understanding of the molecular basis of phagocyte cytotoxicity focusing on two major opsonic receptors on phagocytes, Fc?Rs (receptors for IgG immune complex) and the ¿2 integrin Mac-1 (receptor for complement fragment iC3b). Major accomplishments of the past 4 years were to 1) demonstrate that Vav proteins, exchange factor for Rho GTPase family members are required for several Mac-1 and Fc?R mediated adhesive functions in neutrophils, 2) identify Vav proteins as the major signal transducers of NADPH oxidase activation following Fc?R engagement, through regulation of Rac GTPases and phosphorylation of the NADPH oxidase p40phox, 3) present in vivo evidence that neutrophil Fc?R dependent but not complement dependent tissue injury requires Vav and Rac proteins, 4) define a role for Mac-1 in triggering neutrophil elastase release and subsequent hemorrhagic vasculitis in vivo, through activation of the src and syk kinases, and 5) demonstrate a critical role for Mac-1 on neutrophils in two additional complement dependent models, bullous pemphigoid and thrombotic glomerulonephritis. The current application builds on these discoveries. The objective of Aim I is to delineate mechanisms of neutrophil phagocytosis that are relevant for complement C3 mediated tissue injury and host defense. In particular we will examine both signals that lead to Mac-1 binding of its target and those that link Mac-1 to downstream effector functions. In Aim II, we will further delineate mechanisms of Vav mediated regulation of the NADPH oxidase following Fc?R engagement in neutrophils and macrophages. We will also clarify the role of Vav and Rac in IgG or complement mediated phagocytosis in macrophages in models of autoimmune hemolytic anemia. We anticipate that the completion of our aims should lead to a better understanding of signaling pathways that link opsonic receptors to specific phagocyte cytotoxic functions. This may aid in the design of therapeutics to selectively target pathways responsible for tissue damage in inflammatory and autoimmune disorders while minimizing effects on host defense. PUBLIC HEALTH RELEVANCE: The objective of this proposal is to understand the neutrophil dependent mechanisms that mediate injury to the dermal microvasculature, a well-recognized target of autoimmune damage that contributes to end organ/skin disease. For example, the inflammatory destruction of the vessel wall, vasculitis, is observed in autoimmune rheumatic diseases with cutaneous involvement being the most common, and neutrophil accumulation being a common feature. Drugs such as natalizumab, which interferes with neutrophil trafficking have demonstrated marked therapeutic efficacy in autoimmune diseases, but also exhibited potentially fatal immunosuppression. In this application we propose to delineate signaling pathways that potentially promote microvascular tissue damage, but are not required for neutrophil recruitment. This could lead to the identification of targeted therapeutic strategies that attenuate organ injury while minimally immunocompromising the host.