CD8 T Cell Replicative Senescence: Impact on Aged Humans

这项拟议的研究解决了一系列问题，这些问题是由于老年人一直 在他们的一生中暴露在无数的病原体中。在某些情况下，这种免疫学历史导致了 产生已达到复制衰老阶段的扩增群体的记忆CD8 T细胞。在……里面 细胞培养，CD8T细胞在反复几轮抗原驱动的增殖后达到这种状态，显示出不可逆转的细胞 周期停滞、CD28基因表达永久性丧失、细胞凋亡抵抗、应激反应差、细胞因子改变 与CD28+祖细胞相比，端粒变短。临床研究已经确定了相关性 表现出复制衰老特征的CD8T细胞与多种健康结局之间的关系 对流感疫苗接种和骨质疏松性骨折的反应性。这项拟议研究的中心假设是 体内存在的高比例衰老的CD8 T细胞对免疫和非免疫系统都有有害影响 衰老过程中的免疫器官系统。进一步阐明CD8 T细胞复制的潜在机制 衰老可能会调节多效性生理效应，具体目标如下：(1) 确定衰老CD8 T细胞在免疫功能中的作用。直接细胞相互作用和无细胞培养上清液 将评估衰老培养对CD4T细胞辅助、CD8效应器功能、抗原提呈的影响 和抗体的产生。(2)评价逆转CD8 T细胞复制的遗传和非遗传操作 衰老。含有CD28或端粒酶的慢病毒载体、氧气水平降低和雌激素暴露 (它影响几个与衰老有关的基因)对端粒/端粒酶的影响将进行比较 动态，种群倍增，CD8T细胞免疫功能，和免疫调节功能，在目标1中确定。 (3)基于慢性骨质疏松症的文献记载，探讨衰老的CD8 T细胞在骨质疏松中的作用。 免疫激活对骨骼完整性和骨髓中产生细胞因子的T细胞的鉴定。 早期传代和衰老的CD8T细胞将对成熟、分化和功能的影响进行比较 破骨细胞(骨吸收细胞)和成骨细胞(骨形成细胞)。体外观察将得到证实 使用骨质疏松症的小鼠模型。总之，拟议的研究将提供一个无与伦比的机会 实验解剖了人类免疫衰老的几个基本方面的遗传和分子基础 这对健康和长寿有很大影响。

The proposed research addresses a series of questions that emerge from the fact that elderly persons have been exposed to a myriad of pathogens over their lifespan. This immunological history leads, in some cases, to the generation of expanded populations of memory CD8 T cells that have reached the stage of replicative senescence. In cell culture, CD8 T cells that reach this state after repeated rounds of antigen-driven proliferation show irreversible cell cycle arrest, permanent loss of CD28 gene expression, apoptosis resistance, poor response to stress, altered cytokine profiles, and shortened telomeres compared to their CD28+ progenitors. Clinical studies have identified correlations between CD8 T cells showing characteristics of replicative senescence and such diverse health outcomes as reduced responsiveness to influenza vaccination and osteoporotic fractures. The central hypothesis of the proposed research is that the high proportion of senescent CD8 T cells present in vivo exerts deleterious effects on both immune and non- immune organ systems during aging. To further elucidate the underlying mechanisms by which CD8 T cell replicative senescence may mediate pleiotropic physiological effects, the following specific aims will be addressed: (1) To determine the role of senescent CD8 T cells on immune function. Direct cell interaction and cell-free supernatants from senescent cultures will be evaluated for their impact on CD4 T cell help, CD8 effector functions, antigen-presentation and antibody production. (2) To evaluate genetic and non-genetic manipulations to reverse CD8 T cell replicative senescence. Lentivirus vectors containing CD28 or telomerase, reduced levels of oxygen, and exposure to estrogen (which affects several genes associated with senescence) will be compared for effects on telomere/telomerase dynamics, population doublings, CD8 T cell immune functions, and immune modulatory functions identified in Aim 1. (3) To investigate the role of senescent CD8 T cells in osteoporosis, based on the well-documented effects of chronic immune activation on bone integrity and on the identification of cytokine-producing T cells within the bone marrow. Early passage and senescent CD8 T cells will be compared for effects on the maturation,differentiation, and function of osteoclasts (the bone resorbing cells) and osteoblasts (the bone forming cells). In vitro observations will be confirmed using a murine model of osteoporosis. In sum, the proposed studies will provide an unparalleled opportunity to experimentally dissect the genetic and molecular basis of several fundamental aspects of human immunological aging that significantly impact health and longevity.