Myelin-reactivity of a novel population of T cells infiltrating the normal aging monkey brain

摘要 正常人类衰老的特征是执行功能、学习和记忆甚至 在没有阿尔茨海默病（AD）的神经变性的情况下。虽然这种认知老化是长期的， 认为是由于神经元损失，对无AD的人的体视学研究表明， 不是丢失，而是髓鞘病变增加，白色物质丢失。恒河猴是一种珍贵的 正常衰老的模型，因为他们没有明显的AD神经变性，但仍然表现出认知能力下降 类似于人类。通过对猴子大脑进行认知评估，我们发现， 鞘的分裂和膨胀可能损害轴突传导速度，并可能导致轴突损失， 白色物质体积减少。重要的是，髓鞘病理学与年龄相关的认知障碍相关， 猴子。虽然这种白色物质病理学的潜在机制仍然未知，但我们的实验室发现， 在白色物质中，小胶质细胞的活化和吞噬功能障碍随着年龄的增长而增加， 认知能力下降在研究这个问题的过程中，我最近发现， 伴有外周T细胞浸润到与髓鞘病理学改变相同的部位的白色物质中， 是普遍的。这些结果挑战了大脑是“免疫特权”的概念，相反， 易受外周T细胞浸润，导致自身攻击和继发性炎性损伤。 此外，T细胞不浸润老化的灰质，这表明浸润是组织特异性的， 在与年龄相关的白色物质病理学中发挥作用。这个项目的目标是确定为什么T细胞渗透到 老化的大脑以及它们在软组织中的白色物质中的功能。我将表演一系列 对经过认知测试的恒河猴的脑组织进行实验，以检验与年龄相关的假设 神经炎症导致T细胞的实质浸润，其中它们是髓磷脂反应性的，并有助于 与年龄相关的髓鞘病变在目标1中，我将探索T细胞如何被贩运到大脑中， 以及T细胞如何与髓鞘病理学相关。这将通过使用 免疫组织化学标记T细胞和光谱共聚焦反射（SCoRe）显微镜定量髓鞘。 在目标2中，我将通过使用免疫组织化学方法分析浸润性T细胞的基因表达模式来研究其功能。 RNA测序和评估它们的髓鞘反应性和参与髓鞘损伤， 器官型切片培养。为了实验性地调节T细胞活性，将培养物用两种 靶向T细胞并减少多发性硬化症中髓鞘损伤的治疗剂。除了表征 随着年龄的增长，我将发现浸润性T细胞是否是髓鞘反应性的，如果它们 导致白色物质病理学和认知损害的严重性。这些数据应确定 未来实验和治疗干预的目标，以减缓或防止大脑老化。

ABSTRACT Normal human aging is characterized by cognitive impairments in executive function, learning and memory even in the absence of the neurodegeneration of Alzheimer's Disease (AD). While such cognitive aging was long believed to be due to neuronal loss, stereologic investigations of humans free of AD have shown that neurons are not lost, but instead myelin pathology increases and white matter is lost. The rhesus monkey is a valuable model of normal aging as they are spared the overt neurodegeneration of AD but still exhibit cognitive decline similar to humans. Examining the brains of cognitively assessed monkeys, we have found that the myelin shows splitting and ballooning of sheaths that likely impairs axonal conduction velocity and may lead to axon loss and reduced white matter volume. Importantly, myelin pathology correlates with age-related cognitive impairment in the monkey. While the mechanisms underlying this white matter pathology are still unknown, our lab has found that activation and phagocytic dysfunction of microglia increases in the white matter with age and correlates with cognitive decline. In pursuing this problem, I recently discovered that age-related increases in brain inflammation are accompanied by infiltration of peripheral T cells into the white matter in the same loci where myelin pathology is prevalent. These results challenge the concept that the brain is 'immune privileged' and instead might be vulnerable to infiltration of peripheral T cells leading to auto-attack and secondary inflammatory damage. Moreover, T cells do not infiltrate the aging gray matter, suggesting that infiltration is tissue specific and may play a role in age-related white matter pathology. The goal of this project is to determine why T cells infiltrate the aging brain and what their function is within in the white matter in parenchyma. I will perform a series of experiments on brain tissue from cognitively tested rhesus monkeys to test the hypothesis that age-related neuroinflammation leads to parenchymal infiltration of T cells where they are myelin-reactive and contribute to age-related myelin pathology. In Aim 1, I will explore how T cells are trafficked into the brain, what T cell subtypes are present and how T cells are related to myelin pathology. This will be accomplished using immunohistochemistry to label T cells and spectral confocal reflectance (SCoRe) microscopy to quantify myelin. In Aim 2, I will investigate the function of infiltrating T cells by analyzing their gene expression patterns using RNA sequencing and assessing their myelin reactivity and involvement in myelin sheath damage using organotypic slice cultures. To experimentally modulate T cell activity, the cultures will be treated with two therapeutics that target T cells and reduce damage to myelin in multiple sclerosis. In addition to characterizing brain parenchymal T cells with age, I will discover whether infiltrating T cells are myelin reactive and if they contribute to the white matter pathology and the severity of cognitive impairment. These data should identify targets for future experimental and therapeutic interventions to slow or prevent brain aging.