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，如果创伤患者出现感染性并发症，炎症的增强可以促进全身性炎症性休克。我们已经报道，一种不同的CD4T细胞亚群被称为调节性T细胞(Tregs)，被损伤激活，并有效地抑制T细胞介导的免疫功能和损伤诱导的炎症。因此，我们认为Treg是一种损伤反应细胞亚群，具有控制先天免疫和获得性免疫功能的能力。这个项目中的实验将检验这一假说，并将揭示损伤导致Tregs快速激活的细胞和分子途径。提出了以下具体目标：1.确定Tregs是通过抗原受体依赖还是独立机制被损伤激活。T细胞受体(TCR)与抗原提呈细胞表面MHC II类(MHCII)分子提呈的抗原结合，可特异性激活CD4T细胞。本实验将利用MHCII基因缺陷(MHCII-/-)小鼠、FoxP3-GFP基因敲入小鼠和过继转移方法来解决MHCII依赖Treg激活的问题。先天(MyD88和TRIF)和T细胞共刺激通路(CD40L、CD28和CTLA-4)也将被测试为损伤特异性激活Tregs的潜在MHCII非依赖通路。2.研究Tregs的损伤特异性激活和信号转导机制。烧伤后Tregs的早期激活表明Tregs对损伤反应迅速且具有特异性。在这一目标中，我们建议识别和研究TCR依赖和TCR非依赖的信号通路，这些信号通路在烧伤小鼠的Tregs激活。这一目标的实验将使用磷酸流式细胞术来测量MHCII、TLR、CD28、CD40L或CTLA4依赖的Tregs的激活。3.明确Tregs的伤害特异性回忆反应的特异性和性质。最近的研究发现，Tregs对烧伤表现出一种类似回忆的反应，这支持了Tregs可能对损伤做出特异性反应的观点。这一目标的研究将进一步调查这一基本发现，并将利用这一观察结果来促进我们对损伤特异性免疫反应的理解。这个项目的临床意义在于，这些信息可以用来开发控制严重创伤和手术患者中发生的免疫系统并发症的创新方法。

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.