Function of thymic epithelial cells in T lymphocyte maturation

描述(由申请者提供)：胸腺通过明确的成熟途径发育成多种T细胞系。这些T细胞的成熟需要T细胞前体与胸腺微环境之间的持续相互作用，胸腺微环境由各种基质细胞组成，包括胸腺皮质细胞和髓质上皮细胞(cTECs和mTECs)。现已证实，cTECs在CD4-CD8双阴性胸腺细胞的发育和阳性选择中起关键作用，而mTECs则介导阴性选择和阳性选择后的成熟。然而，cTECs和mTECs向发育中的T细胞的不同阶段和不同谱系传递信号的机制仍不清楚。发育中的T细胞的不同命运可能是由它们与不同的TEC亚群的相互作用决定的。众所周知，cTECs和mTECs表现出广泛的异质性。TECs的高度复杂性有力地支持了TECs的单个亚群在胸腺细胞成熟过程中发挥不同功能的假设。然而，这一假说尚未得到检验，因为它不可能在体内分离组成高度异质性TEC隔室的各种细胞亚群的功能。为了解决这个问题，我们开发了几种小鼠遗传模型，允许在体内和体外选择性地删除不同的TEC亚群。我们已经将由猴白喉毒素受体-绿色荧光蛋白组成的融合蛋白插入到在cTECs或mTECs亚群中表达的单个基因的基因座上。在一个这样的模型中，我们发现注射白喉毒素会导致cTECs的快速删除和胸腺细胞的大量减少，证明了这种方法在评估单个TECs在胸腺细胞成熟中的作用是有效的。在这项建议中，我们将使用这些遗传模型来研究单个TEC亚群在胸腺细胞成熟中的作用。从这些实验中获得的数据将提供关于胸腺细胞-TEC相互作用的有价值的信息，并为识别涉及胸腺细胞发育和选择的新的分子机制提供框架。重要的是，这些遗传模型也是研究胸腺器官发生和再生的细胞调控的宝贵工具。 T淋巴细胞在胸腺中成熟。这一过程取决于胸腺结构提供的微环境。胸腺上皮细胞是胸腺结构的重要组成部分，为T淋巴细胞成熟提供不可或缺的信号。到目前为止，胸腺上皮细胞如何支持T淋巴细胞成熟在很大程度上是未知的。然而，了解胸腺上皮细胞支持T细胞成熟的功能对于我们理解免疫缺陷和自身免疫性疾病是至关重要的，因为胸腺上皮细胞功能障碍导致了这些疾病。我们建议使用遗传小鼠模型来剖析不同群体的胸腺上皮细胞在胸腺细胞成熟过程中的功能。我们的研究结果将帮助我们了解自身免疫性疾病和免疫缺陷是如何发展的。此外，这些模型还可用于研究衰老后的胸腺再生。

DESCRIPTION (provided by applicant): Multiple T cell lineages develop in the thymus through well-defined maturation pathways. The maturation of these T lineage cells requires continuous interaction between T cell precursors and the thymic microenvironment, which consists of various stromal cells including thymic cortical and medullary epithelial cells (cTECs and mTECs, respectively). It has been established that cTECs play critical roles in development of CD4- CD8- double negative thymocytes and positive selection while mTECs mediate negative selection and post-positive selection maturation. However, the mechanisms allowing cTECs and mTECs to deliver signals to different stages and different lineages of developing T cells remain unknown. The different fates of developing T cells are likely determined by their interactions with various subpopulations of TECs. It is well established that cTECs and mTECs display extensive heterogeneity. The highly complex nature of TECs strongly supports the hypothesis that individual subsets of TECs perform distinct functions in thymocyte maturation. However, this hypothesis has not been tested because it has not been possible to separate the function of the various cell subpopulations comprising the highly heterogeneous TEC compartment in vivo. To address this issue, we have developed several mouse genetic models that allow the selective deletion of distinct subpopulations of TECs in vivo and in vitro. We have inserted a fusion protein consisting of simian diphtheria toxin receptor- green fluorescent protein into the loci of individual genes expressed in subsets of cTECs or mTECs. In one such model, we show that injection of diphtheria toxin induces rapid deletion of cTECs and massive reduction in thymocytes, demonstrating the effectiveness of this approach in assessing the role of individual TECs in thymocyte maturation. In this proposal, we will investigate the roles of individual TEC subsets in thymocyte maturation using these genetic models. Data obtained from these experiments will provide valuable information about thymocyte-TEC interactions, and generate a framework for identification of novel molecular mechanisms involved in thymocyte development and selection. Importantly, these genetic models are also valuable tools to study cellular regulation of thymic organogenesis and regeneration.Narrative T lymphocytes undergo maturation in the thymus. This process depends on the microenvironment provided by the thymic structure. Thymic epithelial cells are important constituents of the thymic structure and provide indispensable signals for T lymphocyte maturation. Up to this point, how thymic epithelial cells support T lymphocyte maturation is largely unknown. However, understanding the function of thymic epithelial cells in supporting T cell maturation is essential to our understanding of immunodeficiency and autoimmune diseases as dysfunction of thymic epithelial cells causes these diseases. We propose to use genetic mouse models to dissect the function of different populations of thymic epithelial cells in thymocyte maturation. The results from our studies will help us to understand how autoimmune disease and immunodeficiency develop. In addition, these models can also be used to study thymic regeneration after aging.