Dobbs L G, Gonzalez R F, Allen L, Froh D K
Departments of Medicine and Pediatrics and the Cardiovascular Research Institute, University of California San Francisco, San Francisco, California 94118, USA.
J Histochem Cytochem. 1999 Feb;47(2):129-37. doi: 10.1177/002215549904700202.
The alveolar epithelium is composed of two morphologically distinct types of cells, Type I and Type II cells. The thin cytoplasmic extensions of Type I cells cover more than 95% of the internal surface area of the lungs. Type I cells provide the very short diffusion pathway essential for gas exchange. Because there were no biochemical markers specific for human Type I cells, we developed a strategy to produce a monoclonal antibody (MAb) specific for human Type I cells. Isolated human lung cells were used as immunogens; >5000 clones from seven fusions were screened to identify an MAb specific for a 56-kD protein of Type I cells, HTI56. By Western blotting, HTI56 is unique to the lung. By immunoelectron microscopy, it is localized to the Type I cell apical plasma membrane. The pI of HTI56 is 2.5-3.5. HTI56 is glycosylated and has the biochemical characteristics of an integral membrane protein. HTI56 is detectable by Week 20 of gestation and its expression increases in fetal lung explant culture. HTI56 should be useful as a marker for human Type I cells both morphologically and biochemically. It may also be useful in studies of disease and as a marker for lung injury.
肺泡上皮由两种形态上不同的细胞类型组成，即I型细胞和II型细胞。I型细胞薄的细胞质延伸覆盖了肺内表面积的95%以上。I型细胞提供了气体交换所必需的极短扩散途径。由于没有针对人I型细胞的特异性生化标志物，我们开发了一种策略来制备针对人I型细胞的单克隆抗体（MAb）。分离的人肺细胞用作免疫原；对来自7次融合的5000多个克隆进行筛选，以鉴定出一种针对I型细胞56-kD蛋白（HTI56）的单克隆抗体。通过蛋白质印迹法，HTI56在肺中是独特的。通过免疫电子显微镜观察，它定位于I型细胞顶端质膜。HTI56的等电点为2.5 - 3.5。HTI56是糖基化的，具有整合膜蛋白的生化特征。HTI56在妊娠20周时可检测到，其表达在胎儿肺外植体培养中增加。HTI56在形态学和生物化学方面都应可作为人I型细胞的标志物。它在疾病研究中可能也有用，并且可作为肺损伤的标志物。
