Von Gaudecker B, Kendall M D, Ritter M A
Anatomisches Institut, Christian Albrechts-Universität, Kiel, Germany.
Microsc Res Tech. 1997 Aug 1;38(3):237-49. doi: 10.1002/(SICI)1097-0029(19970801)38:3<237::AID-JEMT5>3.0.CO;2-J.
Normal T cell development depends upon interactions between progenitor cells and the thymic microenvironment. Monoclonal antibodies (Mabs) have been used to define subtypes of thymic epithelium by light microscopy (clusters of thymic epithelial staining [CTES]). We have now used a range of these Mabs together with gold-coupled reagents in immuno-electron microscopy to study the fine cellular distribution of the molecules to which the antibodies bind. Anti-cytokeratin antibodies were used to identify all thymic epithelial cells, while the distribution of MHC class II molecules was revealed with Mabs to shared nonpolymorphic determinants. MR6, a CTES III Mab, shows strong surface labelling of cortical epithelial cells and thymic nurse cells and very weak surface staining of thymocytes, medullary macrophages, and interdigitating cells. Mab 8.18 (CTES V) also labels a cell surface molecule; this is present on Hassall's corpuscles and associated medullary epithelial cells. The molecules detected by Mabs MR6 and 8.18 are therefore located in a position where they are available to interact with external cellular and soluble signals within the thymus. In contrast, Mabs MR10 and MR19 (CTES II) recognise intracellular molecules within subcapsular, perivascular, and medullary epithelium. A similar distribution was seen with Mab 4beta, directed against the thymic hormone thymulin, although, in addition to the expected intracellular epithelial staining, large lymphoblasts in the subcapsular zone showed surface positivity, indicating the presence of thymulin bound to surface receptors on these early lymphoid cells. As expected, MHC class II molecules were expressed on some medullary and essentially all cortical epithelial cells. However, although most subcapsular epithelium was class II-negative, some cells did express these MHC molecules on their apical surface and on the surface of their cytoplasmic extensions into the cortex. Interestingly, some cortical epithelial cells surrounding capillaries were positive for both MR6 (CTES III) and for MR10, MR19, and 4beta (CTES II). Double-labelling experiments, using MR6 and MR19 simultaneously, revealed a double-positive perivascular epithelial cell population in the thymic cortex. The possibility that these cells represent a thymic epithelial progenitor population is discussed.
正常T细胞的发育依赖于祖细胞与胸腺微环境之间的相互作用。单克隆抗体（Mab）已被用于通过光学显微镜（胸腺上皮染色簇[CTES]）来定义胸腺上皮的亚型。我们现在将一系列这些Mab与金偶联试剂一起用于免疫电子显微镜，以研究抗体所结合分子的精细细胞分布。抗细胞角蛋白抗体用于识别所有胸腺上皮细胞，而Mab针对共享的非多态性决定簇揭示了MHC II类分子的分布。MR6，一种CTES III Mab，显示皮质上皮细胞和胸腺哺育细胞有强烈的表面标记，而胸腺细胞、髓质巨噬细胞和交错突细胞的表面染色非常弱。Mab 8.18（CTES V）也标记一种细胞表面分子；它存在于哈氏小体和相关的髓质上皮细胞上。因此，Mab MR6和8.18检测到的分子位于一个可与胸腺内外部细胞和可溶性信号相互作用的位置。相比之下，Mab MR10和MR19（CTES II）识别被膜下、血管周围和髓质上皮内的细胞内分子。针对胸腺激素胸腺素的Mab 4β也观察到类似的分布，尽管除了预期的细胞内上皮染色外，被膜下区的大淋巴细胞显示表面阳性，表明这些早期淋巴细胞表面存在与表面受体结合的胸腺素。正如预期的那样，MHC II类分子在一些髓质和基本上所有皮质上皮细胞上表达。然而，尽管大多数被膜下上皮细胞II类阴性，但一些细胞在其顶端表面以及其细胞质延伸到皮质的表面确实表达了这些MHC分子。有趣的是，一些围绕毛细血管的皮质上皮细胞对MR6（CTES III）以及MR10、MR19和4β（CTES II）均呈阳性。同时使用MR6和MR19的双标记实验揭示了胸腺皮质中血管周围上皮细胞的双阳性群体。讨论了这些细胞代表胸腺上皮祖细胞群体的可能性。
