Function of thymic epithelial cells in T lymphocyte maturation

描述（由申请人提供）：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系细胞的成熟需要T细胞前体和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（分别为cTECs和mTECs）。已经确定ctec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mtec介导阴性选择和后阳性选择成熟。然而，允许ctec和mtec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然未知。发育中的T细胞的不同命运可能是由它们与tec不同亚群的相互作用决定的。ctec和mtec表现出广泛的异质性。TECs高度复杂的性质有力地支持了TECs的个体亚群在胸腺细胞成熟中发挥不同功能的假设。然而，这一假设尚未得到验证，因为不可能在体内分离组成高度异质TEC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删除不同的tec亚群。我们将一种由猿猴白喉毒素受体-绿色荧光蛋白组成的融合蛋白插入到cTECs或mTECs亚群中表达的单个基因位点中。在一个这样的模型中，我们发现注射白喉毒素诱导ctec的快速缺失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方面的有效性。在这一建议中，我们将使用这些遗传模型研究单个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为胸腺细胞- tec相互作用提供有价值的信息，并为鉴定涉及胸腺细胞发育和选择的新分子机制提供框架。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有价值的工具。叙述

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.