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

描述（由申请人提供）：中性粒细胞和巨噬细胞的吞噬功能对微生物感染的免疫至关重要，但在炎症反应和自身免疫病理过程中也可能导致组织损伤。本应用程序的总体目标是继续扩展我们对吞噬细胞细胞毒性的分子基础的理解，重点关注吞噬细胞上的两种主要声速受体Fc？Rs （IgG免疫复合物受体）和¿2整合素Mac-1（补体片段iC3b受体）。过去4年的主要成就是：1)证明了几种Mac-1和Fc -1需要Vav蛋白，Rho GTPase家族成员的交换因子。2)鉴定了Vav蛋白作为Fc？R参与，通过调节Rac gtpase和NADPH氧化酶p40phox的磷酸化，3)在体内提供了中性粒细胞Fc？R依赖而非补体依赖的组织损伤需要Vav和Rac蛋白；4)通过激活src和syk激酶，确定了Mac-1在体内触发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；5)在另外两种补体依赖模型（大疱性类天疱疮和血栓性肾小球肾炎）中，Mac-1对中性粒细胞的关键作用。当前的应用建立在这些发现的基础上。Aim I的目的是描述与补体C3介导的组织损伤和宿主防御相关的中性粒细胞吞噬机制。特别是，我们将研究导致Mac-1结合其目标的信号和那些将Mac-1连接到下游效应功能的信号。在Aim II中，我们将进一步描述Vav介导的Fc？中性粒细胞和巨噬细胞的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中的作用。我们预计，我们的目标的完成应该导致更好地理解信号通路，连接opsonic受体特定的吞噬细胞毒性功能。这可能有助于设计治疗方法，选择性地靶向炎症和自身免疫性疾病中负责组织损伤的途径，同时最大限度地减少对宿主防御的影响。

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.