Interleukin-2 and autoimmune disease

描述(申请人提供)：白细胞介素2(IL-2)是典型的T细胞生长因子，但IL-2的消除会导致严重的免疫失调和全身自身免疫，因为这种细胞因子的必备功能是维持CD4+CD25+FoxP3+调节性T淋巴细胞(Treg)。明确IL-2在Treg维持中的作用，以及在缺乏IL-2的情况下效应细胞和记忆细胞是如何产生的，对于理解这种细胞因子的生物学和由于缺乏Treg(更广泛地说，由于缺少Treg)而导致的疾病的发病机制，以及开发使用这种细胞因子及其拮抗剂作为治疗性免疫反应调节剂的最佳策略是基本的。我们将按照以下具体目标解决这些问题。1.IL-2在维持功能Treg中所起的重要作用的机制是什么？为了验证IL-2的必备功能是防止Treg的凋亡死亡和促进Treg功能相关基因表达的假设，我们将定义在缺乏IL-2信号的情况下在外周和胸腺发育的Treg的表型和功能特征。我们将使用删除细胞因子剥夺的传感器Bim的遗传方法，在缺乏IL-2的情况下产生可存活的Treg。我们将定义这些细胞在体外和体内的功能，并分析这些细胞与在IL-2存在下发育的FoxP3+细胞相比存在缺陷的生化途径。利用逆转录病毒基因转导，我们将检测将IL-2与Treg生存和功能联系起来的生化信号，特别是Akt和Stat5。为了优化IL-2及其拮抗剂的治疗策略，我们将询问不同数量和持续时间的IL-2信号是否会对效应/记忆细胞和Treg产生不同的影响。2.IL-2在效应器和记忆反应中的作用是什么？在缺乏IL-2的情况下，这些反应是如何发展的？为了验证这一假设，即IL-2为激活的T细胞提供克服Treg控制的能力，并且在没有Treg的情况下反应变得不依赖于IL-2，我们将比较正常受者和具有完整淋巴系统的IL-2/CD25xCD28双敲除Treg缺陷小鼠中正常和CD25缺陷T细胞的激活情况。我们还将确定在存在和不存在Treg和IL-2的情况下T细胞激活的生化相关性。我们将使用活体成像方法，在没有Treg的情况下，研究T细胞识别抗原后的早期事件。3.与IL-2缺乏相关的免疫性疾病的基础是什么？IL-2基因敲除的BALB/c小鼠的自身免疫性疾病以快速起病的溶血性贫血和淋巴细胞增殖为特征，并与显著增加的干扰素-g的产生(Th1反应)和树突状细胞(DC)的激活有关。我们将明确增强T细胞细胞因子应答的机制及其在自身免疫性疾病中的作用，并探讨由于缺乏内源性Treg而自发激活DC的可能性。因此，这个项目解决了IL-2功能的基本问题，以及它在激活效应器/记忆反应和Treg中的双重作用是如何协调的。这些研究将有助于阐明免疫调节和耐受的机制，并可能有助于优化IL-2及其拮抗剂的治疗方案。项目简介：白细胞介素2(IL-2)是一种T细胞生长因子，已被用于治疗以增强免疫反应，而IL-2拮抗剂已被用作免疫抑制药以防止移植物排斥反应和治疗移植物抗宿主病。最近的研究结果表明，IL-2具有双重生物学作用，它通过促进效应细胞和记忆细胞的发育来刺激免疫反应，而由于其在维持功能调节性T细胞(Treg)中的重要作用而限制了同样的反应。如果我们要使用IL-2或其拮抗剂作为治疗药物，并了解其在免疫调节中的作用，我们必须阐明其双重功能是如何协调的。该项目使用转基因和基因敲除小鼠模型来确定为什么IL-2是Treg生存和功能所必需的，以及在缺乏IL-2的情况下如何诱导效应器和记忆反应。我们还将分析由于缺乏IL-2而导致的自身免疫性疾病的机制，并确定是否可以使用不同剂量和持续时间的IL-2来差异激活效应细胞和Treg。

DESCRIPTION (provided by applicant): Interleukin-2 (IL-2) is the prototypic T-cell growth factor but elimination of IL-2 results in severe immune dysregulation and systemic autoimmunity because the obligatory function of this cytokine is to maintain CD4+ CD25+ FoxP3+ regulatory T-lymphocytes (Treg). Defining the role of IL-2 in the maintenance of Treg, and how effector and memory cells are generated in the absence of IL-2, is fundamental for understanding the biology of this cytokine and the pathogenesis of diseases caused by its absence (and more generally, by the absence of Treg), and also for developing optimal strategies for using this cytokine and its antagonists as therapeutic immune response modifiers. We will address these issues along the following specific aims. 1. What mechanisms underlie the obligatory role of IL-2 in the maintenance of functional Treg? To test the hypothesis that the obligatory functions of IL-2 are to prevent apoptotic death of Treg and to promote expression of genes involved in Treg function, we will define the phenotypic and functional characterisitics of Treg that develop in the periphery and the thymus in the absence of IL-2 signals. We will use the genetic approach of deleting Bim, the sensor of cytokine deprivation, to generate viable Treg in the absence of IL-2. We will define the functions of these cells in vitro and in vivo, and analyze the biochemical pathways that are defective in these cells compared to FoxP3+ cells that develop in the presence of IL-2. Using retroviral gene transduction, we will examine the biochemical signals that link IL-2 to Treg survival and function, particularly Akt and Stat5. We will ask if different amounts and duration of IL-2 signal differentially affect effector/memory cells vs Treg, in order to optimize strategies for therapeutic use of IL-2 and its antagonists. 2. What is the role of IL-2 in effector and memory responses, and how do these responses develop in the absence of IL-2? To test the hypothesis that IL-2 functions to provide activated T-cells the capacity to overcome Treg control, and responses become IL-2-independent in the absence of Treg, we will compare the activation of normal and CD25-deficient T-cells in normal recipients and in IL-2/CD25xCD28 double-knockout Treg-deficient mice we have developed that have a full lymphoid system. We will also define the biochemical correlates of T-cell activation in the presence and absence of Treg and IL-2. We will examine the early events after T-cell recognition of antigen in the absence of Treg, using in vivo imaging methods. 3. What is the basis of the immunological disease associated with IL-2 deficiency? The autoimmune disease of IL-2-knockout BALB/c mice is characterized by rapid-onset hemolytic anemia and lymphoproliferation, and is associated with markedly enhanced IFN-g production (Th1 responses) and activation of dendritic cells (DCs). We will define the mechanism of the enhanced T-cell cytokine response and its contribution to the autoimmune disease, and explore the possibility that DCs are spontaneously activated b5cause of the absence of endogenous Treg. Thus, this project addresses fundamental issues of the functions of IL-2 and how its dual role in activating effector/memory responses and Treg is orchestrated. These studies will shed light on the mechanisms of immune regulation and tolerance, and may help to optimize protocols for the therapeutic uses of IL-2 and its antagonists.7. PROJECT NARRATIVE: Interleukin-2 (IL-2) is a T-cell growth factor that has been used therapeutically to boost immune responses, and IL-2 antagonists have been used as immunosuppressive agents to prevent rejection of allografts and treat graft-vs-host disease. Recent results have shown that IL-2 has a dual biological role it stimulates immune responses by promoting the development of effector and memory cells, and it limits the same responses by virtue of its essential role in the maintenance of functional regulatory T cells (Treg). If we are to use IL-2 or its antagonists as therapeutic agents, and understand its role in immune regulation, we must elucidate how its dual functions are orchestrated. This project uses transgenic and gene knockout mouse models to define why IL-2 is required for Treg survival and function, and how effector and memory responses can be induced in its absence. We will also analyze the mechanisms of the autoimmune disease caused by the absence of IL-2, and determine if different amounts and duration of IL-2 administration can be used to differentially activate effector cells and Treg.