Studies of selection mechanism against self reactive T cell clones during intrathymic development

在自身免疫性疾病中，某些T细胞克隆与自身成分反应，导致组织的异常反应。在正常动物或人类中，已知在胸腺环境中，这种反应性自身复合物的T细胞在发育途径中被删除，但自身反应性T细胞的删除机制仍不清楚。因此，从分子水平上研究这一机制对于了解自身免疫性疾病的发生具有重要意义。在这个美日合作的项目中，我们试图建立一个适当的实验系统，在其中检查通过胸腺基质细胞的相互作用的特定T细胞的发育。为了在生理条件下获得不同发育阶段的特定T细胞克隆的胸腺细胞，我们尝试制备T细胞抗原受体（TCR）转基因小鼠。同时，我们尝试建立了胸腺基质细胞克隆，并成功地获得了大部分T细胞识别OVA的TRC转基因小鼠。我们还建立了具有胸腺细胞发育诱导功能的胸腺基质细胞克隆。将TCR转基因小鼠胸腺细胞在有卵清蛋白存在的基质细胞克隆上培养。胸腺细胞特异性缺失表明处于CD4^+CD8^+胸腺细胞发育阶段。加入卵清蛋白也可诱导胸腺细胞DNA断裂。这些结果表明，未成熟的胸腺细胞被删除的胸腺细胞凋亡时，他们识别的抗原，这是在生理条件下的自我组成部分。使用我们建立的系统，我们计划确定参与诱导胸腺中对抗原反应的未成熟T细胞缺失的分子。

In autoimmune diseases, certain T cell clones react to self-components, resulting in the abnormal reactions for tissues. In normal animals or human beings, such T cells reacting self-compomets are known to be deleted in the developing pathway in the thymic environment but the deletion mechanism of self-reactive T cells remained unclear. Thus, the study of this mechanism on molecular levelis important for understanding the occurrence of autoimmune diseases. In this project of US-Japan collaboration, we tried to establish an appropriate experimental system in which development of a particular T cells by interaction of thymic stromal cells is examined. For obtaining thymocytes of a particular T cell clone at various developing stages in physiological condition, we tried to produce T cell antigen receptor (TCR) transgenic mice. At the same time, we tried to establish thymic stromal cell clones which are capable of inducing immature thymocytes into mature ones.During the period of this project, we succeeded to obtain TRC transgenic mice in which the majority of T cells recognize OVA. We also established a thymic stromal cell clones possessing inductive functions for thymocyte development. When the thymocytes from TCR transgenic mice were cultured on the stromal cellclone in the presence of OVA. specific deletion of thymocytes were demonstration a CD4^+CD8^+ thymocyte developing stage. DNA fragmentation of the thymocytes were also induced by adding OVA. These results indicate that immature thymocytes are deleted in the thymus by apoptosis when they recognize the antigens, which are self-components in physiological conditions. Using our established system, we are planning to identify the moleculres which are involved in inducing deletion of immature T cells reacting to antigens in the thymus.