Mechanisms of Peripheral Induction of T-Cell Tolerance

T 细胞耐受的外周诱导机制

• 批准号: 7846602
• 负责人: MATTHEW Franklin MESCHER
• 金额: $ 1.45万
• 依托单位: UNIVERSITY OF MINNESOTA
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-05 至 2010-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7846602
• 关键词: Mechanisms; Peripheral; Induction; Cell; Tolerance

DESCRIPTION (provided by applicant): T lymphocytes must respond to specific antigen by rapid proliferation and differentiation to mount an effective immune response. It is critical that this occur only in response to foreign antigen, so that self antigens do not induce autoimmune responses. Tolerance to self-antigen is achieved in part by negative selection in the thymus. This is not complete, however, and some self-reactive T cells escape into the periphery. Mechanisms exist for rendering these mature T cells tolerant, but they are poorly understood. This Program is addressing the nature of these mechanisms in mature T cells using both in vitro and in vivo models. Peripheral tolerance in CD4 T cells is being studied in Projects I (Jenkins) and II (Mueller), and in CD8 T cells in Projects III (Hogquist) and IV (Mescher). Thus, both major subsets of T cells are being studied. In addition, Projects I and III examine CD4 and CD8 T cell tolerance at the biological level using novel models, and Projects II and IV examine tolerance mechanisms in CD4 and CD8 T cells at the molecular levels. The planned work involves extensive collaborative interactions among the investigators. It is anticipated that the findings obtained in these studies will contribute to a better understanding of how autoimmunity is avoided. Understanding of these mechanisms, and hence how to manipulate them, has the potential to contribute to improvements in transplantation and disease therapy. Mechanisms that induce tolerance to self-antigens may also induce tolerance to foreign antigens, including those present on tumors or virus-infected cells, resulting in the immune system failing to mount a protective response. Finally, there is great potential for using defined peptide antigens to induce protective or therapeutic immunity for a broad range of diseases and a great deal of current effort is focusing on this. However, it is becoming increasingly clear that these must be used with great caution since they can also induce tolerance that may lead to lessened protection or exacerbated disease. Thus, developing a better understanding of the mechanisms that can lead to T cell tolerance, as proposed in this Program, has implications well beyond autoimmune diseases. PROJECT 1: Analysis of Peripheral Tolerance in vivo (Jenkins, M.) PROJECT 1 DESCRIPTION (provided by applicant): The long-term goal of this project is an understanding of the mechanisms that account for CD4+ T cell tolerance to antigens that are presented in the secondary lymphoid organs but not the thymus. Previously, we showed that naive CD4+ T cells that are exposed to model antigens in the secondary lymphoid organs in the absence of inflammation proliferate poorly, then most of the progeny die, and the survivors enter an anergic state characterized by poor lymphokine production. The goal of this application is to establish whether or not a similar series of events accounts for peripheral tolerance to certain natural self-proteins. This has become a pressing issue since the discovery that the AIRE transcription factor drives ectopic expression of extrathymic gene products in the thymus. Thus, it remains possible that the physiological role that peripheral tolerance was thought to play is really played by AIRE-mediated intrathymic tolerance. Here, we will test the hypothesis that peripheral tolerance is physiologically-relevant by using new tools to identify the tolerance mechanisms that apply to two pregnancy-specific proteins, one that appears to be regulated by AIRE and another that does not, and one sperm-specific protein. We will determine whether or not these proteins are immunogenic in mice that have never expressed them in the relevant tissue (e.g., non-pregnant female mice), and become non-immunogenic in mice after expression (e.g., pregnant female mice). The relevant antigenic peptides will be identified and used to produce peptide-MHC II multimers. The multimers will then be used with a sensitive new enrichment method capable of detecting fewer than 100 cells per mouse to enumerate peptide MHC II specific CD4+ T cells before, during, and after expression of the relevant protein within the polyclonal repertoires of normal mice. This approach should reveal whether or not the relevant CD4+ T cells are deleted, turn into regulatory cells, or become anergic during or after the period when these developmentally regulated self-proteins are expressed. This approach will then be used in gene-targeted mice to determine whether or not molecules such as Fas and Cbl-b, and others identified by other members of the P01, are involved in the identified tolerance mechanism. Success would provide the first definitive identification of the peripheral tolerance mechanism that applies to a natural self-antigen. This information should help focus future research on the relevant mechanism and shed light on the potential ways that it could fail and lead to autoimmunity.

描述（由申请人提供）：T淋巴细胞必须通过快速增殖和分化对特定抗原做出反应，以产生有效的免疫反应。至关重要的是，这种情况仅发生在对外源抗原的反应中，因此自身抗原不会诱导自身免疫反应。对自身抗原的耐受性部分是通过胸腺中的负选择来实现的。然而，这并不完整，一些自身反应性 T 细胞逃逸到外周。存在使这些成熟 T 细胞耐受的机制，但人们对它们知之甚少。 该计划正在利用体外和体内模型来探讨成熟 T 细胞中这些机制的本质。项目 I (Jenkins) 和 II (Mueller) 正在研究 CD4 T 细胞的外周耐受性，项目 III (Hogquist) 和 IV (Mescher) 正在研究 CD8 T 细胞的外周耐受性。因此，T 细胞的两个主要亚群都在研究中。此外，项目 I 和 III 使用新模型在生物水平上检查 CD4 和 CD8 T 细胞耐受性，项目 II 和 IV 在分子水平上检查 CD4 和 CD8 T 细胞的耐受机制。计划的工作涉及研究人员之间广泛的协作互动。 预计这些研究中获得的结果将有助于更好地了解如何避免自身免疫。了解这些机制以及如何操纵它们有可能有助于改善移植和疾病治疗。诱发机制 对自身抗原的耐受性也可能诱导对外来抗原的耐受性，包括肿瘤或病毒感染细胞上存在的抗原，导致免疫系统无法产生保护性反应。最后，使用确定的肽抗原来诱导针对多种疾病的保护性或治疗性免疫具有巨大的潜力，并且当前的大量工作都集中在这一点上。然而，越来越清楚的是，必须非常谨慎地使用这些药物，因为它们也会引起耐受性，从而导致保护减弱或疾病加剧。因此，正如本计划所提出的那样，更好地了解导致 T 细胞耐受的机制，其意义远远超出了自身免疫性疾病的范围。 项目 1：体内外周耐受性分析 (Jenkins, M.) 项目 1 描述（由申请人提供）：该项目的长期目标是了解 CD4+ T 细胞对次级淋巴器官而非胸腺中存在的抗原的耐受性机制。此前，我们发现，在没有炎症的情况下，在次级淋巴器官中暴露于模型抗原的幼稚CD4+T细胞增殖不良，然后大多数后代死亡，幸存者进入以淋巴因子产生不良为特征的无能状态。该应用的目标是确定一系列类似的事件是否解释了对某些天然自身蛋白的外周耐受。自从发现 AIRE 转录因子驱动胸腺中胸腺外基因产物的异位表达以来，这已成为一个紧迫的问题。因此，外周耐受性被认为发挥的生理作用实际上是由 AIRE 介导的胸腺内耐受性发挥的。在这里，我们将通过使用新工具来确定适用于两种妊娠特异性蛋白质（一种似乎受 AIRE 调节，另一种不受 AIRE 调节）以及一种精子特异性蛋白质的耐受机制，来检验外周耐受性与生理相关的假设。我们将确定这些蛋白在从未在相关组织中表达过的小鼠（例如，非怀孕雌性小鼠）中是否具有免疫原性，以及在表达后在小鼠（例如，怀孕雌性小鼠）中是否变得非免疫原性。相关的抗原肽将 被鉴定并用于生产肽-MHC II 多聚体。然后，多聚体将与一种灵敏的新富集方法一起使用，该方法能够检测每只小鼠少于 100 个细胞，以在多克隆内相关蛋白表达之前、期间和之后计数肽 MHC II 特异性 CD4+ T 细胞 正常小鼠的曲目。这种方法应该揭示相关的 CD4+ T 细胞是否在这些发育调节自身蛋白表达期间或之后被删除、转变为调节细胞或变得无反应。然后，这种方法将用于基因靶向小鼠，以确定 Fas 和 Cbl-b 等分子以及 P01 其他成员识别的其他分子是否参与已识别的耐受机制。成功将首次明确鉴定适用于天然自身抗原的外周耐受机制。这些信息应有助于将未来的研究重点放在相关机制上，并揭示其可能失败并导致自身免疫的潜在方式。