Birkenbach M, Tong X, Bradbury L E, Tedder T F, Kieff E
Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115.
J Exp Med. 1992 Nov 1;176(5):1405-14. doi: 10.1084/jem.176.5.1405.
Epstein-Barr virus (EBV) adsorption to human B lymphocytes is mediated by the viral envelope glycoprotein, gp350/220, which binds to the cell surface protein, CD21, also known as the CR2 complement receptor. Human epithelial cells also express an EBV receptor. A candidate surface molecule of 195 kD has previously been identified on an epithelial cell line and explanted epithelial tissue by reactivity with the CD21 specific monoclonal antibody (mAb), HB-5a. In experiments to further characterize the epithelial cell EBV receptor, we have found that two human epithelial cell lines, RHEK-1 and HeLa, specifically bind intact EB virions. A 145-kD protein, similar in size to B lymphocyte CD21, was specifically precipitated from surface iodinated RHEK-1 cells using the HB-5a mAb, or using purified soluble gp350/220 coupled to agarose beads. The previously identified 195-kD protein did not bind to gp350/220 or react with two other anti-CD21 mAbs. CD21 homologous RNA, similar in size to the B lymphocyte CD21 mRNA, was detected in both RHEK-1 and HeLa cells. The nucleotide sequence of the epithelial cell cDNA was identical to B lymphocyte CD21. The longest clone differs from previously reported CD21 cDNAs in having additional 5' untranslated sequence. Polymerase chain reaction amplification of RHEK-1- or B lymphoblastoid-derived cDNA verified that most CD21 transcripts are initiated at least 30-50 nucleotides upstream of the previously reported mRNA cap site. These experiments demonstrate that human epithelial cells can express CD21, and that CD21 is likely to mediate EBV adsorption to epithelial cells.
爱泼斯坦-巴尔病毒（EBV）对人B淋巴细胞的吸附由病毒包膜糖蛋白gp350/220介导，该糖蛋白与细胞表面蛋白CD21结合，CD21也被称为CR2补体受体。人上皮细胞也表达EBV受体。先前已通过与CD21特异性单克隆抗体（mAb）HB-5a反应，在一种上皮细胞系和外植的上皮组织中鉴定出一个195 kD的候选表面分子。在进一步表征上皮细胞EBV受体的实验中，我们发现两种人上皮细胞系RHEK-1和HeLa能特异性结合完整的EB病毒颗粒。使用HB-5a mAb或与琼脂糖珠偶联的纯化可溶性gp350/220，从表面碘化的RHEK-1细胞中特异性沉淀出一种大小与B淋巴细胞CD21相似的145-kD蛋白。先前鉴定的195-kD蛋白不与gp350/220结合，也不与另外两种抗CD21 mAb反应。在RHEK-1和HeLa细胞中均检测到大小与B淋巴细胞CD21 mRNA相似的CD21同源RNA。上皮细胞cDNA的核苷酸序列与B淋巴细胞CD21相同。最长的克隆与先前报道的CD21 cDNA的不同之处在于有额外的5'非翻译序列。对RHEK-1或B淋巴母细胞来源的cDNA进行聚合酶链反应扩增，证实大多数CD21转录本在先前报道的mRNA帽位点上游至少30 - 50个核苷酸处起始。这些实验表明人上皮细胞可以表达CD21，并且CD21可能介导EBV对上皮细胞的吸附。
