Investigating aging and membrane-associated T cell receptor signaling in human CD

描述（由申请人提供）：随着年龄的增长，T细胞免疫发生改变，导致感染和恶性肿瘤的风险增加。T细胞通过T细胞受体（TCR）识别抗原呈递细胞（APCs）呈递的抗原肽，从而激活T细胞。这种TCR触发在T细胞中诱导一系列生化事件，称为信号转导，这是T细胞功能所必需的。有趣的是，在小鼠和人类中，TCR信号转导的年龄相关改变已被报道，与T细胞功能受损有关。然而，在大多数人体研究中，尽管存在不同的CD4+和CD8+ T细胞亚群，如na - ve和记忆细胞，具有不同的功能，并且na - ve和记忆CD4+和CD8+ T细胞的比例随着年龄的增长而改变，但仍使用未分类的总CD4+或CD8+ T细胞。最近，我的实验室测量了IL-7受体α链（IL-7Ra, CD127）的表达，IL-7是一种对T细胞稳态至关重要的细胞因子，它决定了年轻人和老年人CD8+ T细胞对IL-7的反应。本研究在记忆性CD8+ T细胞中发现IL-7Rahigh和low表达的细胞。令人惊讶的是，老年人（65岁）比年轻人（40岁）有il - 7low记忆CD8+ T细胞的扩增。IL-7Ra低记忆性CD8+ T细胞在TCR触发时增殖不良，表明这些细胞中存在TCR信号缺陷，IL-7Ra作为识别TCR反应受损的记忆性CD8+ T细胞的标记物的潜在作用。有趣的是，il - 7low记忆性CD8+ T细胞在TCR触发和IL-15（记忆性CD8+ T细胞维持所必需的细胞因子）的联合作用下增殖良好。这表明IL-15在恢复il - 7low记忆CD8+ T细胞受损的TCR信号转导中起作用。了解这些发现的机制很重要，因为记忆性CD8+ T细胞对宿主防御至关重要，而IL-15被认为是细胞免疫的辅助剂。该研究将基于以下假设来解决这些问题：随着年龄的增长，il -7低记忆CD8+ T细胞在TCR信号转导中存在缺陷，而这些缺陷可以通过IL-15来修复。我们将利用共聚焦显微镜和流式细胞术对一组与T细胞膜密切相关的TCR信号分子进行研究。具体而言，计划实现以下两个目标。首先，研究il - 7低记忆CD8+ T细胞随着年龄的增长是否以及为什么在TCR信号转导中存在缺陷。此外，其他CD8+ T细胞亚群中TCR信号转导的改变以及CD8+ T细胞亚群中TCR信号转导缺陷的潜在机制将通过测量细胞膜胆固醇含量和T细胞表面分子的糖基化来研究，这些分子已知会随着年龄的增长影响TCR信号转导。其次，将确定IL-15如何在il - 7low memory CD8+ T细胞中修复受损的TCR信号转导。这项研究的结果将提供必要的信息，从而通过增强细胞免疫来更好地保护老年人免受肿瘤和感染。当前提案的目标是研究衰老如何影响CD8+ T细胞通过其受体（T细胞受体）从外部向内部传递刺激（信号转导）的分子。这项研究的结果将为增强老年人的免疫反应提供重要信息，从而提高对感染和肿瘤的保护。

DESCRIPTION (provided by applicant): Alterations in T cell immunity occur with aging, contributing to increased risk of infection and malignancy. T cells are activated as they recognize antigenic peptide presented by antigen-presenting cells (APCs) via T cell receptors (TCR). This TCR triggering induces a series of biochemical events called signal transduction in T cells which are essential for T cell functions. Of interest, age-associated alterations in TCR signal transduction have been reported in mice and humans, linking to impaired T cell functions. However, in most human studies unsorted total CD4+ or CD8+ T cells have been used although different CD4+ and CD8+ T cell subsets, such as na¿ve and memory cells, with distinct functions exist and the proportion of na¿ve and memory CD4+ and CD8+ T cells alters with aging. Recently, my lab measured expression of IL-7 receptor alpha chain (IL-7Ra, CD127) which dictates the response to IL-7, a cytokine critical for T cell homeostasis, on CD8+ T cells in young and elderly individuals. In this study, cells expressing IL-7Rahigh and low were found in memory CD8+ T cells. Surprisingly, the elderly (age=65) had expansion of IL-7Ralow memory CD8+ T cells compared to the young (age=40). IL-7Ralow memory CD8+ T cells poorly proliferated in response to TCR triggering, indicating a TCR signaling defect(s) in these cells and the potential role for IL-7Ra as a marker for identifying memory CD8+ T cells with impaired TCR responses. Of interest, IL-7Ralow memory CD8+ T cells nicely proliferate in response to a combination of TCR triggering and IL-15, a cytokine essential for memory CD8+ T cell maintenance. This suggests a role for IL-15 in recovering the impaired TCR signal transduction in IL-7Ralow memory CD8+ T cells. Understanding the mechanism(s) for these findings is important since memory CD8+ T cells are essential for host defense and IL-15 is considered as an adjuvant for cellular immunity. The proposed study will address these issues based on the hypothesis that expanded IL-7Ralow memory CD8+ T cells with aging have a defect(s) in TCR signal transduction which can be rescued by IL-15. This hypothesis will be investigated focusing on a group of TCR signaling molecules that are closely associated with T cell membrane using confocal microscopy and flow cytometry. Specifically, following two aims are planned. First, investigate whether and why IL-7Ralow memory CD8+ T cells that expand with aging have a defect(s) in TCR signal transduction. Plus, alteration(s) in TCR signal transduction of other CD8+ T cell subsets and the potential mechanisms for defective TCR signal transduction in the CD8+ T cell subsets will be studied by measuring cholesterol content of the cell membrane and glycosylation of T cell surface molecules that are known to affect TCR signal transduction with aging. Secondly, it will be determined how IL-15 rescues impaired TCR signal transduction in IL-7Ralow memory CD8+ T cells. The results of this study will provide essential information that leads to better protection against tumors and infections in the elderly by enhancing cellular immunity. The goal of the current proposal is to study how aging affects the molecules involved in transmitting stimulations from the outside to the inside (signal transduction) of CD8+ T cells through their receptors (T cell receptor). The results of this study will provide important information on enhancing immune responses in the aged populations, leading to improved protection against infections and tumors.