Innate immune cell interactions mediated by the SIRP receptor family

在脊椎动物中，多个系统协作以确保识别和消除老化、缺陷或感染的细胞，同时保留正常的“自我”组织。免疫稳态需要激活受体促进反应和抑制受体维持自我耐受性之间的平衡。我的项目的长期目标是了解这些激活和抑制反应是如何整合的，以保持准确的自我/非自我识别。这种相互作用已经在介导适应性免疫的淋巴细胞中得到了广泛的研究，但在先天免疫细胞如巨噬细胞（M?）中却知之甚少。我们已经证明，先天免疫受体信号调节蛋白-α (SIRPα)是一种抑制性受体，可以识别几乎所有健康细胞上表达的蛋白质。我建议确定SIRPα抑制M？对正常自我的反应，并被调节以允许对非自我细胞作出适当的反应。******SIRPα的配体CD47是广泛表达的细胞表面蛋白“自我标记”。CD47与SIRPα结合，产生“不要吃我”，抑制M？吞噬和炎症介质的分泌。激活受体已经进化到确保识别和清除老化、癌变或病原体感染的细胞。CD47在衰老或受损细胞中的表达减少，sirp α介导的抑制信号减弱，并允许吞噬细胞清除目标细胞。该计划的目标是使用SIRPα作为模型系统来确定抑制信号如何传递以控制巨噬细胞反应，以及这些信号如何与激活受体结合。******通过定义明确的磷酸激酶级联激活受体信号。例如，M？协调吞噬反应通过免疫球蛋白Fc受体的激活信号。相比之下，SIRPα的抑制性信号传导是磷酸酶驱动的，尚未得到很好的理解。这种知识差距是由于缺乏对磷酸酶活性的测定而加剧的。我们将使用流式细胞术来定义sirp α介导的信号传导，通过抗体检测关键激酶、磷酸酶和衔接蛋白上的磷酸化表位。此外，我们将使用一种基因功能缺失的方法来鉴定M？来源于在磷酸酶和衔接蛋白中有种系突变的小鼠。我们的长期目标是确定先天免疫细胞如何平衡激活和抑制信号来清除病原体，并限制对宿主组织的附带损害。这些研究为分析适用于许多系统的先天免疫抑制信号提供了一个范例，并将揭示病原体颠覆宿主机制的新机制，以确保其持久性

In vertebrates, multiple systems collaborate to ensure recognition and elimination of cells that are aged, defective or infected, while preserving normal “self” tissues. Immune homeostasis requires a balance between activating receptors that promote responses and inhibitory receptors that maintain self-tolerance. The long-term goal of my program is to understand how these activating and inhibitory responses are integrated to maintain accurate self/non-self recognition. This interplay has been studied extensively in lymphocytes that mediate adaptive immunity, but is less well understood in innate immune cells such as macrophages (M?). We have shown that the innate immune receptor Signal Regulatory Protein-α (SIRPα) is an inhibitory receptor that recognizes a protein expressed on virtually all healthy cells. I propose to identify the signalling pathways and down-stream mediators by which SIRPα inhibits M? responses to normal self and is regulated to allow appropriate responses to non-self cells. ******SIRPα's ligand CD47 is a widely expressed cell surface protein “marker of self”. CD47 binds to the SIRPα producing a “don't-eat-me” that restrains M? phagocytosis and secretion of inflammatory mediators. Activating receptors have evolved to ensure recognition and removal of aged, cancerous or pathogen-infected cells. CD47 expression is reduced on aged or damaged cells diminishing SIRPα-mediated inhibitory signals, and allowing phagocytic removal of the target cell. The goal of the proposed program is to use SIRPα as a model system to determine how inhibitory signals are conveyed to control macrophage responses, and how these are integrated with activating receptors.******Activating receptors signal through well-defined phospho-kinase cascades. For example, M? orchestrate phagocytosis in response to activating signals through immunoglobulin Fc receptors. In contrast, inhibitory signalling by SIRPα is phosphatase-driven and not well understood. This knowledge gap is fuelled by a paucity of assays for phosphatase activity. We will use flow cytometry to define SIRPα-mediated signalling with antibodies that detect phospho-epitopes on critical kinases, phosphatases and adaptor proteins. In addition, we will use a genetic loss-of-function approach to identify the protein partners of SIRPα signalling in M? derived from mice with germ line mutations in phosphatases and adaptor proteins. Our long term goal is to define how innate immune cells balance activating and inhibitory signals to clear pathogens and also limit collateral damage to host tissues. The studies provide a paradigm for analysis of innate immune inhibitory signalling applicable to many systems, and will uncover new mechanisms of pathogen subversion of host mechanisms to ensure their persistence.**