Fina L, Molgaard H V, Robertson D, Bradley N J, Monaghan P, Delia D, Sutherland D R, Baker M A, Greaves M F
Leukaemia Research Fund Centre, Institute of Cancer Research, London, UK.
Blood. 1990 Jun 15;75(12):2417-26.
All seven of a set of CD34 monoclonal antibodies that recognize epitopes on an approximately 110 Kd glycoprotein on human hemopoietic progenitor cells also bind to vascular endothelium. Capillaries of most tissues are CD34 positive, as are umbilical artery and, to a lesser extent, vein, but the endothelium of most large vessels and the endothelium of placental sinuses are not. Angioblastoma cells and parafollicular mesenchymal cells in fetal skin are also CD34 positive, as are some stromal elements. An approximately 110 Kd protein can be identified by Western blot analysis with CD34 antibodies in detergent extracts of freshly isolated umbilical vessel endothelial cells, and CD34 mRNA is present in cultured umbilical vein cells as well as other tissues rich in vascular endothelium (breast, placenta). These data indicate that the binding of CD34 antibodies to vascular endothelium is to the CD34 gene product, and not to crossreactive epitopes. Despite the presence of CD34 mRNA in cultured, proliferating endothelial cells, the latter do not bind CD34 antibodies. In addition, CD34 antigen cannot be upregulated by growth factors. We conclude that under these conditions, CD34 protein is downregulated or processed into another form that is unreactive with CD34 antibodies. Electron microscopy of umbilical artery, breast, and kidney capillary vessels reveals that in all three sites, CD34 molecules are concentrated on membrane processes, many of which interdigitate between adjacent endothelial cells. However, well-established endothelial cell contacts with tight junctions are CD34 negative. CD34 may function as an adhesion molecule on both endothelial cells and hematopoietic progenitors.
一组能识别人类造血祖细胞上约110 Kd糖蛋白表位的CD34单克隆抗体，全部也能与血管内皮细胞结合。大多数组织的毛细血管呈CD34阳性，脐动脉以及程度稍轻的脐静脉也是如此，但大多数大血管的内皮细胞和胎盘血窦的内皮细胞则不然。胎儿皮肤中的成血管细胞瘤细胞和滤泡旁间充质细胞也呈CD34阳性，一些基质成分也是如此。通过用CD34抗体进行蛋白质印迹分析，可在新鲜分离的脐血管内皮细胞的去污剂提取物中鉴定出一种约110 Kd的蛋白质，并且CD34 mRNA存在于培养的脐静脉细胞以及其他富含血管内皮的组织（乳腺、胎盘）中。这些数据表明，CD34抗体与血管内皮细胞的结合是针对CD34基因产物，而非交叉反应性表位。尽管在培养的增殖性内皮细胞中存在CD34 mRNA，但后者不结合CD34抗体。此外，生长因子不能上调CD34抗原。我们得出结论，在这些条件下，CD34蛋白被下调或加工成了另一种与CD34抗体无反应的形式。对脐动脉、乳腺和肾毛细血管进行电子显微镜检查发现，在所有这三个部位，CD34分子都集中在膜突上，其中许多在相邻内皮细胞之间相互交错。然而，已形成紧密连接的成熟内皮细胞接触部位呈CD34阴性。CD34可能在内皮细胞和造血祖细胞上均作为一种黏附分子发挥作用。
