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

项目摘要/摘要 CD4辅助T(Th)细胞负责宿主对吞噬病原体的免疫并增强抗体 以及细胞毒性T细胞介导的反应。它们也会引起自身免疫，并参与免疫 对肿瘤的反应。TH细胞通过使用抗原受体(TCR)识别这些功能 由与主要组织相容性复合体II类分子(MHCII)结合的多肽(P)组成的表位 显示在各种宿主细胞上。荧光标记的p：MHCII四聚体和流式细胞术已经成为关键 研究表位特异性多克隆Th细胞免疫反应的工具。然而，情况已经变得很明显， P：MHCII四聚体在相关亲和谱的低端不能检测到TCR。这一限制具有 造成了关于具有低亲和力TCR的Th细胞在免疫反应中扮演的角色的知识鸿沟 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域表现不佳。 不与Th细胞上的CD4分子结合。我们用分子进化的方法选择了一个MHCII分子 改进的CD4结合(MHCII-4E)，发现p：MHCII-4E四聚体优于传统试剂 检测低亲和力TCRs的Th细胞。我们将使用这些创新试剂来确定Th 具有低亲和力TCR的细胞在持续和慢性感染的免疫反应中发挥作用，以及自身免疫 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-4e的疫苗 模特。这些目标的完成将填补关于赛尔夫剧目组成的基本知识空白 和外来表位，并为针对低亲和力Th细胞的新疗法提供原则证据。

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.