HLA-DO / H2-O: modulation of MHC-II peptide diversity and Treg population control

HLA-DO / H2-O（DO）是一种非经典的MHCII蛋白，其功能是作为HLA-DO/H2-O（DO）的特异性竞争性抑制剂。 肽交换因子HLA-DM / H2-M（DM），调节抗原中MHCII分子上的肽负载， 呈递细胞在CD 4 T细胞发育过程中，胸腺细胞被选择转化为常规的幼稚T细胞。 CD 4 T细胞或自身耐受性调节性T细胞，或通过阴性选择被删除，这取决于强度 与胸腺中抗原呈递细胞上展示的MHCII结合肽的相互作用。我们洗脱了 来自野生型C57 BL/6和DO敲除胸腺的肽，并发现肽谱的改变 由MHCII分子呈现。我们检测了DO缺陷小鼠中CD 4 T细胞的发育，发现 Treg数量和功能的改变，以及对病毒感染的敏感性增加。总体假设 DO通过抑制DM的肽编辑活性来调节抗原呈递， 为了允许在细胞表面呈现的肽的广泛代表性，这种活性对于 对自身耐受的常规和调节性T细胞进行适当的胸腺选择。有两个具体目标。要求1 目的是评价DO依赖性抗原呈递在选择CD 4 Tconv和Treg群体中的作用。 我们将鉴定在存在或不存在DO的情况下胸腺中差异呈递的肽， 单个TCR克隆型在WT和DO-KO TCR限制性小鼠中进行胸腺选择时，联合收割机 这些结果鉴定了负责Treg偏斜的DO肽，并最终表征了 DO-KO小鼠中的Treg失调。这些实验将检验缩窄肽 由DO缺失诱导的MHCII分子呈递的库导致改变的胸腺选择， 调节性T细胞的外周调节。目的2：探讨HLA-DO / H2-O在Tconv调节中的作用 感染模型中的Treg群体。我们将评估DO诱导的功能性后果， 在BL/6小鼠应答中TCR库和CD 4 T细胞群活化状态的变化 原发性流感感染以前已经显示TcB调节CD 4和CD 8 T细胞应答， 募集先天效应细胞，我们观察到这些效应在DO-KO小鼠中的改变，表明 在不存在DO的情况下TdR的失调。我们将测试这一假设，使用FoxP 3-DTR系统交换 小鼠之间的Treg区室。这一目标的第二部分是评估DO的功能后果， 使用流感感染模型诱导抗原呈递和TCR库的改变。很长的- 本项目的长期目标是确定DO如何控制DM介导的肽编辑来调节选择 自身和病原体衍生的肽展示在MHCII上，并破译DO调节的影响。 肽呈递对CD 4 T细胞库的发育和功能的影响。 1

HLA-DO / H2-O (DO) is a non-classical MHCII protein that functions as a specific competitive inhibitor of the peptide exchange factor HLA-DM / H2-M (DM), regulating peptide loading onto MHCII molecules in antigen- presenting cells. During CD4 T cell development, thymocytes are selected for conversion to conventional naïve CD4 T cells or self-tolerant regulatory T cells, or are deleted by negative selection, depending on the strength of interaction with MHCII-bound peptides displayed on antigen presenting cells in the thymus. We eluted peptides from wild-type C57BL/6 and DO-knockout thymus, and found alterations in the spectrum of peptides presented by MHCII molecules. We examined CD4 T cell development in DO-deficient mice, and found alterations in Treg number and function, and increased sensitivity to viral infection. The overarching hypothesis of this proposal is that DO regulates antigen presentation by restraining the peptide editing activity of DM in order to allow a broad representation of peptides presented at the cell surface, and this activity is essential for proper thymic selection of self-tolerant conventional and regulatory T cells. There are two specific aims. Aim 1 is to evaluate the role of DO-dependent antigen presentation in selection of CD4 Tconv and Treg populations. We will identify peptides differentially presented in the thymus in the presence or absence of DO, follow individual TCR clonotypes as they undergo thymic selection in WT and DO-KO TCR-restricted mice, combine these results to identity DO-peptides responsible for Treg skewing, and finally characterize functional effects of Treg dysregulation in DO-KO mice. These experiments will test the hypothesis that narrowing of the peptide repertoire presented by MHCII molecules induced by deletion of DO results in altered thymic selection and peripheral regulation of regulatory T cells. Aim 2 is to determine the role of HLA-DO / H2-O in regulating Tconv and Treg populations in an infection model. We will evaluate the functional consequences of DO-induced changes in the TCR repertoire and activation state of CD4 T cell populations in the response of BL/6 mice to primary influenza infection. Tregs have been shown previously to regulate CD4 and CD8 T cell responses and recruitment of innate effector cells, and we observe alterations in these effects in DO-KO mice, suggesting a dysregulation of Tregs in the absence of DO. We will test this hypothesis, using a FoxP3-DTR system to swap Treg compartments between mice. A second part of this aim is to evaluate the functional consequences of DO- induced alterations in antigen presentation and TCR repertoires using the influenza infection model. The long- term goals of this project are to define how control of DM-mediated peptide editing by DO regulates selection of self- and pathogen-derived peptides displayed on MHCII, and to decipher the impact of DO-regulated peptide presentation on the development and function of the CD4 T cell repertoire. 1