CD8 T Cell Replicative Senescence: Impact on Aged Humans

拟议的研究解决了一系列问题，这些问题来自老年人一直被 在它们的生命周期中暴露在无数的病原体中。在某些情况下，这种免疫学史导致 产生已达到复制性衰老阶段的记忆性CD 8 T细胞的扩增群体。在 在细胞培养中，在重复的抗原驱动的增殖轮之后达到这种状态的CD 8 T细胞显示出不可逆的细胞增殖。 周期停滞、CD 28基因表达永久性丧失、凋亡抗性、对应激反应差、细胞因子改变 与它们的CD 28+祖细胞相比，它们的端粒缩短。临床研究已经发现 表现出复制性衰老特征的CD 8 T细胞与诸如减少 对流感疫苗接种的反应性和骨质疏松性骨折。拟议研究的中心假设是 体内存在的高比例的衰老CD 8 T细胞对免疫和非免疫细胞都产生有害影响。 免疫器官系统在衰老过程中。为了进一步阐明CD 8 T细胞复制的潜在机制， 衰老可能介导多效性生理效应，以下具体目标将被解决：（1） 确定衰老的CD 8 T细胞对免疫功能的作用。直接细胞相互作用和无细胞上清液 将评估衰老培养物对CD 4 T细胞辅助、CD 8效应子功能、抗原呈递 和抗体生产。(2)评估逆转CD 8 T细胞复制的遗传和非遗传操作， 衰老含CD 28或端粒酶的慢病毒载体、氧水平降低和暴露于雌激素 （影响与衰老相关的几个基因）将比较对端粒/端粒酶的影响。 动力学、群体倍增、CD 8 T细胞免疫功能和目的1中鉴定的免疫调节功能。 (3)根据慢性骨质疏松症的良好记录效应，研究衰老的CD 8 T细胞在骨质疏松症中的作用。 免疫激活对骨完整性和对骨髓内产生精氨酸的T细胞的鉴定的影响。 将比较早期传代和衰老的CD 8 T细胞对CD 8 T细胞的成熟、分化和功能的影响。 破骨细胞（骨吸收细胞）和成骨细胞（骨形成细胞）。将确认体外观察结果 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， 实验性地剖析了人类免疫衰老的几个基本方面的遗传和分子基础 对健康和寿命有重大影响。

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.