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

描述（由申请人提供）：T细胞免疫力的改变随着年龄的增长而发生，导致感染和恶性肿瘤风险增加。当T细胞识别由抗原呈递细胞（APC）通过T细胞受体（TCR）呈递的抗原肽时，T细胞被激活。这种TCR触发诱导T细胞中称为信号转导的一系列生物化学事件，其对于T细胞功能是必需的。令人感兴趣的是，在小鼠和人类中已经报道了TCR信号转导中与年龄相关的改变，其与受损的T细胞功能有关。然而，在大多数人类研究中，使用了未分选的总CD 4+或CD 8 + T细胞，尽管存在具有不同功能的不同CD 4+和CD 8 + T细胞亚群，如幼稚和记忆细胞，并且幼稚和记忆CD 4+和CD 8 + T细胞的比例随着年龄的增长而改变。最近，我的实验室测量了IL-7受体α链（IL-7 Ra，CD 127）的表达，该链决定了对年轻和老年个体中CD 8 + T细胞上IL-7（一种对T细胞稳态至关重要的细胞因子）的反应。在这项研究中，在记忆性CD 8 + T细胞中发现表达IL-7 Ra高和低的细胞。令人惊讶的是，与年轻人（年龄=40）相比，老年人（年龄=65）具有IL-7 Ralow记忆CD 8 + T细胞的扩增。IL-7 Ra低记忆性CD 8 + T细胞响应于TCR触发而增殖不良，表明这些细胞中的TCR信号传导缺陷以及IL-7 Ra作为鉴定具有受损TCR应答的记忆性CD 8 + T细胞的标志物的潜在作用。令人感兴趣的是，IL-7 Ralow记忆性CD 8 + T细胞响应于TCR触发和IL-15（一种对记忆性CD 8 + T细胞维持必不可少的细胞因子）的组合而良好地增殖。这表明IL-15在恢复IL-7 Ralow记忆CD 8 + T细胞中受损的TCR信号转导中的作用。理解这些发现的机制是重要的，因为记忆CD 8 + T细胞对于宿主防御是必需的，并且IL-15被认为是细胞免疫的佐剂。所提出的研究将基于以下假设来解决这些问题：随着衰老而扩增的IL-7 Ralow记忆CD 8 + T细胞在TCR信号转导中具有缺陷，其可以被IL-15拯救。这一假设将研究集中在一组TCR信号分子，是密切相关的T细胞膜，使用共聚焦显微镜和流式细胞术。具体而言，计划实现以下两个目标。首先，研究随着衰老而扩增的IL-7 Ralow记忆性CD 8 + T细胞是否以及为什么在TCR信号转导中存在缺陷。此外，通过测量细胞膜的胆固醇含量和已知随着衰老影响TCR信号转导的T细胞表面分子的糖基化，将研究其他CD 8 + T细胞亚群的TCR信号转导的改变和CD 8 + T细胞亚群中缺陷TCR信号转导的潜在机制。其次，将确定IL-15如何拯救IL-7低记忆性CD 8 + T细胞中受损的TCR信号转导。这项研究的结果将提供重要的信息，通过增强细胞免疫力，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参与通过其受体（T细胞受体）将刺激从CD 8 + T细胞的外部传递到内部（信号转导）的分子。这项研究的结果将为增强老年人群的免疫反应提供重要信息，从而改善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.