Detection and Activation of CD4+ T cells with Low Affinity TCRs

项目总结/摘要 CD 4+辅助性T（Th）细胞负责宿主对吞噬体病原体的免疫并增加抗体 和细胞毒性T细胞介导的应答。它们还引起自身免疫，并可参与免疫应答。 对肿瘤的反应。Th细胞通过使用抗原受体（TCR）识别 表位由与主要组织相容性复合体II类分子（MHCII）结合的肽（p）组成 展示在各种宿主细胞上。荧光染料标记的p：MHCII四聚体和流式细胞术已经成为关键 用于研究表位特异性多克隆Th细胞的免疫应答的工具。然而，很明显， p：MHCII四聚体不能检测到相关亲和谱低端的TCR。这种局限性 造成了关于具有低亲和力TCR的Th细胞在免疫应答中所起作用的知识空白， 感染和癌症。我们假设p：MHCII四聚体表现不佳是因为它们的茎区 不与Th细胞上的CD 4分子结合。我们使用分子进化来选择MHCII分子， 改进的CD 4结合（MHCII-4 E），并发现p：MHCII-4 E四聚体优于常规试剂上级 检测具有低亲和力TCR的Th细胞。我们将使用这些创新的试剂来确定Th 具有低亲和力TCR的细胞在对持续性和慢性感染的免疫应答中起作用， 中枢神经系统疾病。我们还将在B细胞白血病中测试基于p：MHCII-4 E的疫苗 模型这些目标的完成将填补有关Th曲目组成的基本知识空白 和外源表位，并为靶向低亲和力Th细胞的新疗法提供原理证明。

Project Summary/Abstract CD4+ helper T (Th) cells are responsible for host immunity to phagosomal pathogens and augment antibody and cytotoxic T cell-mediated responses. They also cause autoimmunity and can participate in immune responses to tumors. Th cells carry out these functions by using antigen receptors (TCRs) to recognize epitopes consisting of peptides (p) bound to major histocompatibility complex class II molecules (MHCII) displayed on various host cells. Fluorochrome-labeled p:MHCII tetramers and flow cytometry have been critical tools for studying immune responses by epitope-specific polyclonal Th cells. It has become clear, however, that p:MHCII tetramers do not detect TCRs at the low end of the relevant affinity spectrum. This limitation has created a knowledge gap about the roles that Th cells with low-affinity TCRs play in immune responses to infections and cancer. We hypothesized that p:MHCII tetramers underperform because their stalk regions do not bind to CD4 molecules on Th cells. We used molecular evolution to select an MHCII molecule with improved CD4 binding (MHCII-4E) and found that p:MHCII-4E tetramers are superior to conventional reagents at detecting Th cells with low affinity TCRs. We will use these innovative reagents to identify the roles that Th cells with low affinity TCRs play in immune responses to persistent and chronic infections, and an autoimmune disease of the central nervous system. We will also test a p:MHCII-4E-based vaccine in a B cell leukemia model. Completion of these aims will fill basic knowledge gaps about the composition of Th repertoires for self and foreign epitopes and provide proof of principle for new therapies targeted to low affinity Th cells.