Study of Tenascin-C on the thymocyte differentiation in mice

TN-C是最大的细胞外基质蛋白之一，在成年小鼠的胸腺和脾中有相当程度的表达。为了探讨TN-C在免疫系统中的作用，我们对TN-C缺陷的C3H/HEN同源小鼠进行了亚致死性X射线照射。照射后第1周，TN-C基因缺陷小鼠胸腺细胞系阴性-CD44暗阳性-CD25阳性胸腺细胞较野生型提前1天消失。这强烈表明，TN-C抑制了X-射线低敏感性胸腺T细胞的分化，而胸腺T细胞被认为是胸腺重建的主要来源。我们对野生型小鼠的胸腺进行了生化和免疫组织化学分析。在混合淋巴细胞反应(MLR)的功能分析中，来自TN-C缺陷的GRS/A的应答细胞对野生型BALB/c刺激细胞的反应性明显低于TN-C缺陷的BALB/c。这一发现为我们提供了两种可能性：一种是TN-C通过某些抑制因子或信号全面抑制MLR，另一种是TN-C抑制MLR特异性T细胞克隆的形成。为了阐明后一种可能性，我们分析了TN-C缺陷和野生型GRS/A小鼠外周淋巴结T细胞的T细胞受体β链(Vβ)的表达。然而，我们找不到它们之间的任何区别。相反，对来自非刺激脾和淋巴结的记忆/激活T细胞的FACS分析表明，TN-C的存在可能改变了外周记忆T细胞的诱导。

Tenascin-C (TN-C), one of the biggest extracellular matrix proteins, is expressed at considerable levels in the thymuses and spleens of adult mice. In order to investigate the function of TN-C in the immune system, we subjected TN-C deficient C3H/HeN congenic mice to sublethal X-irradiation. In the first week after irradiation, we found lineage negative-CD44 dull positive-CD25 positive thymocytes of TN-C deficient mice disappeared one day earlier than those of wild type mice. This strongly suggests that TN-C suppresses the differentiation of X-ray low sensitive thymic T cells which are believed as the major source of thymus reconstitution. We analyzed thymuses of wild-type mice biochemically and immunohistochemically. The expression of TN-C elevated strongly within a week after irradiation, and its expression was observed primarily at intra medullary lymphocytes and cortical blood vessels.On the functional assay using mixed lymphocyte reaction (MLR) method, responder cells from TN-C deficient GRS/A showed significantly low response to the stimulator cells from wild-type BALB/c than those from TN-C deficient BALB/c. This finding brought us the two possibilities ; one is that TN-C suppressed MLR overall via some suppressive factors or signals, and another is that TN-C worked to decrease the development of MLR reactive specific T cell clones. In order to clarify the latter possibility, we analyzed the T cell receptor β chain (Vβ) expression of peripheral lymph node T cells from TN-C deficient and wild-type GRS/A mice. However, we could not find any difference between them. On the contrary, FACS analyses of memory/activated T cells from non-stimulated spleens and lymph nodes indicated that the existence of TN-C might modify the induction of peripheral memory T cells.