Innate and Adaptive Immune Consequences of Necroptosis

提案摘要 先天免疫系统对感染引起的组织稳态的扰动作出反应， 死亡细胞和组织损伤。细胞通过不同的程序性细胞死亡模式死亡，包括细胞凋亡和 坏死性凋亡细胞凋亡导致的细胞死亡是健康组织生理学的正常组成部分， 分裂和维持正常的组织大小和功能。细胞凋亡导致的细胞死亡是致耐受性的， 炎症性坏死性凋亡，与病理性和炎症性坏死性凋亡形成对比。坏死性上睑下垂涉及 形成受体相互作用丝氨酸/苏氨酸蛋白激酶RIPK 1、RIPK 3和 坏死性凋亡效应物混合谱系激酶结构域样蛋白（MLKL）。直到最近，坏死性凋亡被认为是 主要在控制感染方面发挥作用，主要是作为一种防故障策略， 凋亡然而，对小鼠模型的研究表明，细胞凋亡组分的缺乏， 半胱天冬酶-8或FADD等机制导致胚胎死亡，由坏死性凋亡驱动，并依赖于 RIPK 3和MLKL。在肠上皮中使用半胱天冬酶-8或FADD的条件性缺失的其他研究 显示阻断介导稳态细胞凋亡的途径会导致肠道炎症 与RIPK 3水平升高和坏死性凋亡相关。事实上，程序性细胞死亡的显著增加 肠上皮细胞（IEC）的表达在炎症性肠病（IBD）患者中已有报道， 损伤与炎症加剧和肿瘤坏死因子（TNF）-a水平升高有关， 细胞死亡的重要介质。使用一种新的小鼠模型，我们可以诱导触发IEC的坏死性凋亡， 我们将确定IEC坏死性凋亡如何影响肠道内稳态，我们将定义IEC坏死性凋亡的性质。 炎症反应。我们以前的工作已经确定，肠内稳态凋亡 上皮细胞是免疫抑制和耐受的主要驱动力， (MNP)具有“抑制炎症”和“诱导调节性CD 4 T细胞”转录特征。这里 我们将定义坏死性凋亡如何影响MNP反应。我们将研究的组成和特点 小肠MNP群体对坏死性IEC有反应，并在各种先天性免疫缺陷中解释其功能， 与炎症介质的产生、先天性淋巴样细胞的调节有关的免疫功能 功能以及CD 4 T辅助细胞分化。我们所获得的知识将解释坏死性凋亡 通过先天和适应性细胞群驱动炎症反应，作为 其他组织坏死性凋亡的后果，并为开发新的治疗方法奠定基础 慢性炎症性疾病如IBD。

PROPOSAL SUMMARY The innate immune system responds to perturbations in tissue homeostasis resultant from infection but also dying cells and tissue damage. Cells die by different modes of programmed cell death including apoptosis and necroptosis. Cell death by apoptosis is a normal component of healthy tissue physiology that is balanced by cell division and maintains normal tissue size and function. Cell death by apoptosis is tolerogenic and non- inflammatory, and contrasts with necroptosis, which is pathological and inflammatory. Necroptosis involves the formation of a complex of receptor interacting serine/threonine protein kinases RIPK1, RIPK3 and the necroptosis effector mixed lineage kinase domain-like protein (MLKL). Up until recently, necroptosis was thought to function primarily in the control of infection and mainly as a fail-safe strategy that counters viral blockade of apoptosis. Studies in mouse models, however, have shown that deficiency in components of the apoptosis machinery such as caspase-8 or FADD leads to embryonic lethality driven by necroptosis and dependent on RIPK3 and MLKL. Other studies using conditional deletion of caspase-8 or FADD in the intestinal epithelium revealed that blocking the pathways that mediate homeostatic apoptosis precipitates intestinal inflammation associated with elevated levels of RIPK3 and necroptosis. Indeed, a notable increase in programmed cell death of intestinal epithelial cells (IEC) has been reported in patients with inflammatory bowel disease (IBD), and this damage is associated with heightened inflammation and increased levels of tumor necrosis factor (TNF)-a, an important mediator of cell death. Using a novel mouse model where we can inducibly trigger necroptosis of IEC, we will determine how IEC necroptosis impacts intestinal homeostasis and we will define the nature of the inflammatory response. Our previous work has established that homeostatic apoptosis within the intestinal epithelium is a major driver of immune suppression and tolerance, imprinting intestinal mononuclear phagocytes (MNP) with ‘suppression of inflammation’ and ‘induction of regulatory CD4 T cell’ transcriptional signatures. Here we will define how necroptosis impacts MNP responses. We will examine the composition and characteristics of the small intestinal MNP population that responds to necroptotic IEC and decipher its function in various innate immune functions relating to the production of inflammatory mediators, modulation of innate lymphoid cell function as well as the CD4 T helper cell differentiation. The knowledge we gain will define how necroptosis drives inflammatory responses by innate and adaptive populations of cells, serve as a roadmap for the consequences of necroptosis in other tissues, and lay the foundation for the development of novel therapeutics for chronic inflammatory diseases such as IBD.