Injury-Specific Activation of the Immune System

描述（由申请人提供）：严重损伤后免疫系统的炎症和抗炎行为支配着危重损伤患者的临床轨迹。例如，显性抗炎表型会抑制正常的抗微生物免疫，使宿主容易受到机会性感染。另一方面，如果受伤患者出现感染性并发症，炎症的增强可促进全身性炎症休克。我们已经报道了CD4 T细胞的一个独特亚群，称为调节性T细胞（Tregs），可被损伤激活，并有效抑制T细胞介导的免疫功能和损伤诱导的炎症。因此，我们认为Tregs作为一种损伤反应细胞亚群，具有控制先天和适应性免疫功能的能力。该项目的实验将验证这一假设，并揭示损伤导致Tregs快速激活的细胞和分子途径。提出了以下具体目标：以确定treg是否通过抗原受体依赖或独立的机制被激活。CD4 T细胞通过T细胞受体（TCR）结合抗原呈递细胞表面MHCII类（MHCII）分子特异性激活。本实验将使用MHCII基因缺陷（MHCII-/-）小鼠、FoxP3-GFP基因敲入小鼠和过继转移方法来研究MHCII对Treg激活的依赖性。先天（MyD88和TRIF）和T细胞共刺激通路（CD40L， CD28和CTLA-4）也将作为潜在的MHCII独立通路，用于损伤特异性激活Tregs。表征treg的损伤特异性激活和信号传导。烧伤后Tregs的早期激活表明Tregs对损伤有快速和特异性的反应。为此，我们提出鉴定和研究烧伤小鼠treg中激活的tcr依赖性和tcr非依赖性信号通路。本目的实验将使用磷酸流式细胞术来测量MHCII-， TLR-, CD28-， CD40L-或ctla4依赖性Tregs的激活。定义treg损伤特异性回忆反应的特异性和性质。最近发现Tregs对烧伤表现出类似回忆的反应，这支持了Tregs可能对损伤有特异性反应的观点。这方面的研究将进一步研究这一基本发现，并利用这一观察结果促进我们对损伤特异性免疫反应的理解。该项目的临床意义在于，这些信息可用于开发创新方法，以控制发生在严重受伤的创伤和手术患者中的免疫系统并发症。

DESCRIPTION (provided by applicant): The inflammatory and counter-inflammatory behavior of the immune system following severe injury governs the clinical trajectory of critically-injured patients. For example, a dominant counter- inflammatory phenotype will suppress normal anti-microbial immunity and predispose the host to opportunistic infections. On the other hand, augmentation of inflammation can promote systemic inflammatory shock if infectious complications occur in injured patients. We have reported that a distinct subset of CD4 T cells called regulatory T cells (Tregs) are activated by injury and act to potently suppress both T cell mediated immune function and injury-induced inflammation. Thus, we suggest that Tregs act as an injury-reactive cell subset with the capacity to control both innate and adaptive immune function. The experiments in this project will test this hypothesis and will uncover the cellular and molecular pathways responsible for the rapid activation of Tregs by injury. The following specific aims are proposed: 1. to determine if Tregs are activated by injury by antigen receptor dependent or independent mechanisms. CD4 T cells are specifically activated by T cell receptor (TCR) binding to antigens presented by cell-surface MHC class II (MHCII) molecules on antigen presenting cells. The experiments in this aim will address the MHCII-dependence on Treg activation using MHCII gene deficient (MHCII-/-) mice, FoxP3-GFP gene knock-in mice, and adoptive transfer approaches. Innate (MyD88 and TRIF) and T cell costimulatory pathways (CD40L, CD28, and CTLA-4) will also be tested as potential MHCII independent pathways for the injury-specific activation of Tregs. 2. To characterize injury-specific activation and signaling by Tregs. The early activation of Tregs by burn injury suggests that Tregs respond rapidly and specifically to injury. In this aim, we propose to identify and study TCR-dependent and TCR-independent signaling pathways that are activated in Tregs by burn injury in mice. The experiments in this aim will use phospho-flow cytometry to measure MHCII-, TLR-, CD28-, CD40L-, or CTLA4-dependent activation of Tregs. 3. To define the specificity and nature of injury-specific recall responses by Tregs. The recent discovery that Tregs display a recall memory-like response to burn injury supports the idea that Tregs may respond specifically to injury. Studies in this aim will further investigate this basic finding and will use this observation to advance our understanding of injury-specific immune responses. The clinical significance of this project is that this information could be used to develop innovative approaches for controlling the immune system complications that occur in critically-injured trauma and surgical patients.