Function of thymic epithelial cells in T lymphocyte maturation

描述（由申请方提供）：多种T细胞谱系通过明确的成熟途径在胸腺中发育。这些T谱系细胞的成熟需要T细胞前体与胸腺微环境之间的持续相互作用，胸腺微环境由包括胸腺皮质和髓质上皮细胞（分别为cTEC和mTEC）的各种基质细胞组成。已经确定cTECs在CD 4-CD 8-双阴性胸腺细胞的发育和阳性选择中起关键作用，而mTECs介导阴性选择和阳性选择后成熟。然而，允许cTECs和mTECs将信号传递到发育中的T细胞的不同阶段和不同谱系的机制仍然未知。发育中的T细胞的不同命运可能由它们与TEC的各种亚群的相互作用决定。已经确定cTEC和mTEC显示出广泛的异质性。TEC的高度复杂的性质强烈支持的假设，个别的TEC亚群执行不同的功能，胸腺细胞的成熟。然而，该假设尚未得到检验，因为尚不可能在体内分离构成高度异质性TEC区室的各种细胞亚群的功能。为了解决这个问题，我们已经开发了几种小鼠遗传模型，允许在体内和体外选择性删除不同的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cTEC或mTEC亚群中表达的单个基因的位点中。在一个这样的模型中，我们表明，注射白喉毒素诱导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的有效性。在这个建议中，我们将调查的作用，个别TEC亚群在胸腺细胞成熟使用这些遗传模型。从这些实验中获得的数据将提供有价值的信息，胸腺细胞TEC的相互作用，并产生一个框架，用于识别新的分子机制参与胸腺细胞的发展和选择。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节的有价值的工具。Narrative T淋巴细胞在胸腺中成熟。这一过程依赖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，理解胸腺上皮细胞在支持T细胞成熟中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这些疾病。我们建议使用遗传小鼠模型来解剖胸腺上皮细胞在胸腺细胞成熟中的不同群体的功能。我们的研究结果将有助于我们了解自身免疫性疾病和免疫缺陷是如何发展的。此外，这些模型也可用于研究胸腺老化后的再生。

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.