Recent Thymic Emigrants of the CD4 T-cell Lineage

描述（由申请人提供）：表达抗原的幼稚CD4α-T细胞受体对于产生针对新抗原的免疫应答至关重要，并且在胸腺内作为成熟CD4+CD8-胸腺细胞从头产生。它们进入外周，成为幼稚 CD4 T 细胞区室的新胸腺移民 (RTE)。尽管监测 CD4 RTE 具有很大的临床意义，特别是在 CD4 T 细胞淋巴细胞减少症中，但由于缺乏特定的表面标记，对人类 CD4 RTE 的直接评估受到限制。该项目将利用一种新的、最近发现的人类 CD4 RTE 表面标记物——蛋白酪氨酸激酶 7 (PTK7)，来定义 CD4 RTE 频率、表型和功能。初步结果验证了 PTK7 作为 CD4 RTE 标记物，并表明与 PTK7-naive CD4 T 细胞相比，PTK7 CD4 RTE 的效应功能能力降低。目标 1 将通过对未刺激和刺激的 PTK7 CD4 RTE 和其他 CD4 T 谱系细胞进行深度 mRNA 测序来进行基因表达谱分析，以：1) 确定个体发育过程中 PTK7 CD4 RTE 中残留胸腺细胞基因表达的程度，2) 识别参与降低的 CD4 RTE 免疫功能的基因产物，特别是对于 Th1 代和/或将 PTK7 CD4 RTE 细分为更多与更少近期胸腺的基因产物移民。目标 2 将使用体内标记来检验 PTK7 CD4 RTE 是 PTK7 幼稚 CD4 T 细胞的直接前体这一假设，并将确定 PTK7 CD4 RTE 在维持 HIV-1 感染中幼稚 CD4 T 细胞数量和 12-TCR 库多样性方面的作用。目标 3 将使用类似的方法来测试 PTK7 CD4 RTE 在同种异体造血干细胞移植后幼稚 CD4 T 细胞免疫重建中的重要性。目标 4 将定义儿童和成人完全胸腺切除术后 PTK7 CD4 RTE 丢失的动力学，以及这种丢失对初始 CD4 T 细胞数量和 12-TCR 库多样性的影响。总之，这些研究将大大增强我们对胸腺 RTE 产生在维持外周幼稚 CD4 T 细胞区室健康和疾病中的作用的理解。 公共卫生相关性：胸腺产生新的 CD4 T 细胞（也称为 CD4 最近胸腺移出物 (RTE)）对于免疫系统对感染和疫苗做出反应非常重要。这项研究将评估健康个体以及患有可能改变 RTE 产生的疾病或治疗的患者中 CD4 RTE 的产生和功能；这些知识还将有助于识别可能受益于增加 RTE 产量的药物治疗的患者。

DESCRIPTION (provided by applicant): Antigenically naive CD4 expressing a¿-T cell receptors are critical for generating immune responses to neoantigens, and are produced de novo within the thymus as mature CD4+CD8- thymocytes. These enter the periphery to become recent thymic emigrants (RTEs) of the naive CD4 T-cell compartment. Although monitoring of CD4 RTEs is of great clinical interest, particularly in CD4 T-cell lymphopenia, direct evaluation of human CD4 RTEs has been limited by a lack of specific surface markers. This project will utilize a novel and recently identified surface marker for human CD4 RTEs, protein tyrosine kinase 7 (PTK7), to define CD4 RTE frequency, phenotype, and function. Preliminary results validate PTK7 as a CD4 RTE marker, and show that PTK7+ CD4 RTEs have a reduced capacity for effector function compared to PTK7- naive CD4 T cells. Aim 1 will use gene expression profiling by deep mRNA sequencing of unstimulated and stimulated PTK7+ CD4 RTEs and other CD4 T-lineage cells to: 1) define the extent of residual thymocyte gene expression in PTK7+ CD4 RTEs during ontogeny, and 2) identify gene products involved in reduced CD4 RTE immune function, particularly for Th1 generation and/or that subdivide PTK7+ CD4 RTEs into more versus less recent thymic emigrants. Aim 2 will use in vivo labeling to test the hypothesis that PTK7+ CD4 RTEs are the direct precursors of PTK7- naive CD4 T cells, and will determine the role of PTK7+ CD4 RTEs in maintaining naive CD4 T-cell numbers and 12-TCR repertoire diversity in HIV-1 infection. Aim 3 will use a similar approach to test the importance of PTK7+ CD4 RTEs in immune reconstitution of naive CD4 T cells after allogeneic hematopoietic stem cell transplantation. Aim 4 will define the kinetics of loss of PTK7+ CD4 RTEs in children and adults following complete thymectomy and the impact of this loss on naive CD4 T-cell numbers and 12- TCR repertoire diversity. Together, these studies will substantially enhance our understanding of the role of thymic RTE production in maintaining the peripheral naive CD4 T-cell compartment in health and disease. PUBLIC HEALTH RELEVANCE: The production of new CD4 T cells by the thymus, which are also known as CD4 recent thymic emigrants (RTEs), is important for the immune system to respond to infections and vaccines. This research will evaluate the production and function of CD4 RTEs, in healthy individuals and in patients with diseases or treatments that may alter RTE production; this knowledge will also help identify patients that might benefit by treatment with drugs to increase RTE production.