Identification of the complement decay-accelerating factor (DAF) on epithelium and glandular cells and in body fluids.
Identification of the complement decay-accelerating factor (DAF) on epithelium and glandular cells and in body fluids.
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DOI：
10.1084/jem.165.3.848
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发表时间：
1987-03-01
期刊：
影响因子：
--
通讯作者：
Nussenzweig V
中科院分区：
文献类型：
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作者：
Medof ME;Walter EI;Rutgers JL;Knowles DM;Nussenzweig V
衰变加速因子（Decay-Accelerating Factor，DIF）是一种分子量为70 kD的膜调节蛋白，可阻止细胞表面自体补体的激活。使用免疫组化方法和放射免疫测定的基础上单克隆抗体的抗ESTA，我们发现大量的膜相关ESTA抗原的上皮表面的角膜，结膜，口腔和胃肠道粘膜，外分泌腺，肾小管，输尿管和膀胱，宫颈和子宫粘膜，胸膜，心包和滑膜浆膜。此外，我们还在血浆、泪液、唾液和尿液以及滑液和脑脊液中检测到可溶性抗CD 4抗原。虽然血浆、泪液和唾液中的蛋白质通过蛋白质印迹分析大于红细胞（Ehu）膜上的蛋白质，但尿中的蛋白质略小于（67，000）。与纯化的Ehu蛋白质不同，尿中的蛋白质无法掺入红细胞膜。虽然其对补体酶C3-转化酶的抑制活性低于Ehu β，但其与血清C4结合蛋白（C4 bp）的抑制活性相当。使用培养的包皮上皮细胞和Hela细胞进行的生物合成研究显示，其水平（约2 × 10（5）分子/细胞）超过了血细胞。此外，这些研究揭示了两种β-淀粉样蛋白的合成，一种具有与上皮细胞膜β-淀粉样蛋白相对应的表观Mr，另一种具有与尿β-淀粉样蛋白相对应的表观Mr，这表明尿β-淀粉样蛋白变体来自相邻的上皮细胞。体液中的C4 bp的功能尚不清楚，但观察到尿C4 bp具有C4 bp-（或因子H-）样活性，表明其可抑制级联反应的液相激活。
Decay-accelerating factor (DAF) is a 70 kD membrane regulatory protein that prevents the activation of autologous complement on cell surfaces. Using immunohistochemical methods and a radioimmunometric assay based on mAbs to DAF, we found large amounts of membrane-associated DAF antigen on the epithelial surface of cornea, conjunctiva, oral and gastrointestinal mucosa, exocrine glands, renal tubules, ureter and bladder, cervical and uterine mucosa, and pleural, pericardial and synovial serosa. Additionally, we detected soluble DAF antigen in plasma, tears, saliva, and urine, as well as in synovial and cerebrospinal fluids. While plasma, tear, and saliva DAF are larger than erythrocyte (Ehu) membrane DAF by Western blot analysis, urine DAF is slightly smaller (67,000) in Mr. Unlike purified Ehu DAF, however, urine DAF is unable to incorporate into the membrane of red cells. Although its inhibitory activity on the complement enzyme C3-convertase is lower than that of Ehu DAF, it is comparable to that of serum C4 binding protein (C4bp). Biosynthetic studies using cultured foreskin epithelium and Hela cells disclosed DAF levels (approximately 2 X 10(5) molecules/cell) exceeding those on blood cells. In addition, these studies revealed the synthesis of two DAF species, one with apparent Mr corresponding to that of epithelial cell membrane DAF and the other to urine DAF, suggesting that the urine DAF variant arises from adjacent epithelium. The function of DAF in body fluids is unknown, but the observation that urine DAF has C4bp-(or factor H-)like activity shows that it could inhibit the fluid phase activation of the cascade.