Identification of a Damaging Subset of Neutrophils that Arises in Septic Patients

摘要： 脓毒症是“由宿主对感染的反应失调引起的危及生命的器官功能障碍”。 中性粒细胞在脓毒症中变得过度活跃，它们介导了许多发病率和死亡率 与疾病有关。然而，嗜中性粒细胞的抗微生物功能提供了益处， 脓毒症患者的整个中性粒细胞群的耗尽将具有免疫抑制作用。 近来在包括癌症和狼疮的疾病状态中描述了嗜中性粒细胞的异质性。我们 实验室发现血流中存在少量过度表达的中性粒细胞 ICU患者和脓毒症实验动物中整合素VLA 3（CD 49 c/CD 29; a3 b1）。我们已经表明 中性粒细胞VLA 3的阻断或基因耗竭在脓毒症小鼠中具有存活优势。这些发现 表明选择性去除VLA 3高亚群改善了结果而不损害先天宿主 防御感染。在人类中，来自脓毒症患者的中性粒细胞表现出对 通过VLA 3阻断阻止体外内皮细胞的屏障功能。这表明，主要 VLA 3 high细胞对脓毒症宿主的损伤靶点是脉管系统。此外，初步证据还显示， 表明，在疾病晚期具有VLA 3高中性粒细胞的脓毒症患者死亡率增加， 与血液中未显示VLA 3 high细胞的患者相比。总体假设是 在这个提议中测试的是一个独特的，高度炎症和破坏性的血液中性粒细胞亚群， 其表达高水平的VLA 3，在ICU脓毒症患者的循环中出现。是 进一步假设循环中VLA 3高中性粒细胞的存在预测疾病的严重程度， 通过临床评分确定，并且VLA 3代表了用于减轻炎症性细胞因子的可药物化靶点。 同时避免明显的免疫抑制。提出了三个具体的目标来检验 这些假设。目的1将确定VLA 3表达与外周血淋巴细胞活化之间的相关性。 败血症ICU患者的血液中性粒细胞和疾病严重程度。AIM 2将使用人类细胞和多光子 脓毒症小鼠的成像，以检验VLA 3高中性粒细胞包含高度炎症亚群的假设 导致血管损伤和毛细血管渗漏目的3将表征VLA 3高和VLA 3低中性粒细胞 亚群，并检查其损害内皮屏障功能的机制。综合起来看， 这一建议涉及宿主反应失调如何威胁患者生存的机制 并提供了一个分子靶点，用于抑制过度炎症反应的破坏性武器， 保护免疫防御的有益方面。

ABSTRACT: Sepsis is a “life-threatening organ dysfunction caused by a dysregulated host response to infection”. Neutrophils become hyperactive during sepsis and they mediate much of the morbidity and mortality associated with the disease. However the antimicrobial function of neutrophils provides benefit such that depletion of the entire population of neutrophils in the septic patient would be immunosuppressive. Heterogeneity of neutrophils has recently been described in disease states including cancer and lupus. Our laboratories have discovered the presence of a small population of bloodstream neutrophils that overexpress the integrin VLA3 (CD49c/CD29; a3b1) in ICU patients and experimental animals with sepsis. We have shown that blockade or genetic depletion of neutrophil VLA3 has a survival advantage in septic mice. These findings indicate that selective removal of the VLA3high subset improves outcome without impairment of innate host defense against infection. In humans, neutrophils from septic patients demonstrate pronounced damage to the barrier function of endothelial cells in vitro which is prevented by VLA3 blocking. This suggests that the primary target of damage to the septic host by VLA3high cells is the vasculature. In addition, preliminary evidence also shows that septic patients that have VLA3high neutrophils late into the disease have increased mortality as compared to patients who do not show VLA3high cells in their blood. The overarching hypothesis to be tested in this proposal is that a distinct, hyperinflammatory and damaging subset of blood neutrophils, which express high levels of VLA3, arises in the circulation of ICU patients with sepsis. It is hypothesized further that the presence of circulating VLA3high neutrophils predicts severity of the disease as determined by clinical scoring, and that VLA3 represents a druggable target for attenuation of inflammatory damage to the septic patient while avoiding overt immunosuppression. Three specific aims are put forth to test these hypotheses. Aim 1 will determine the correlation between VLA3 expression and activation on peripheral blood neutrophils and illness severity in septic ICU patients. Aim 2 will use human cells and multiphoton imaging of septic mice to test the hypothesis that VLA3high neutrophils comprise a hyperinflammatory subset that causes vascular damage and capillary leak. Aim 3 will characterize the VLA3high and VLA3low neutrophil subsets and examine the mechanisms through which they impair endothelial barrier function. Taken together, this proposal addresses mechanisms regarding how the dysregulated host response threatens patient survival and offers a molecular target for dampening the destructive arms of the hyperinflammatory response while preserving the beneficial aspects of immune defense.