Hamawy M M, Oliver C, Siraganian R P
Clinical Immunology Section, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892.
J Immunol. 1992 Jan 15;148(2):524-31.
A mAb was isolated (mAb BD6) that recognized a surface glycoprotein on rat basophilic leukemia cells (RBL-2H3). The antibody bound to 2 x 10(6) molecules/cell and specifically blocked IgE binding (50% inhibition with 3.48 +/- 0.51 micrograms/ml; mean +/- SEM), although neither IgE nor anti-high affinity IgE receptor (anti-Fc epsilon RI) mAb blocked mAb BD6 binding to the cells. mAb BD6 did not affect the rate of dissociation of cell-bound IgE, nor did it induce or inhibit the internalization of IgE. mAb BD6 did not release histamine. However, it did cause rapid spreading of the cells. By 1 h the cells had retracted to a spherical shape with their surface covered with membranous spikes, and they could easily be detached from the tissue culture plate. These changes differed from those observed after Fc epsilon RI activation. mAb BD6 immunoprecipitated a complex of two proteins, 38 to 50 kDa and 135 kDa from 125I-surface labeled rat basophilic leukemia cells that are not subunits of Fc epsilon RI. Chemical cross-linking studies showed that these molecules are associated on the cell surface. By immunoblotting, mAb BD6 reacted with a 40-kDa protein. Therefore, mAb BD6 binds to a surface protein that is close to the Fc epsilon RI and sterically inhibits 125I-IgE binding.
分离出一种单克隆抗体（mAb BD6），它能识别大鼠嗜碱性白血病细胞（RBL-2H3）表面的一种糖蛋白。该抗体以2×10⁶个分子/细胞的量结合，且能特异性阻断IgE结合（3.48±0.51微克/毫升时50%抑制；平均值±标准误），尽管IgE和抗高亲和力IgE受体（抗FcεRI）单克隆抗体均不能阻断mAb BD6与细胞的结合。mAb BD6不影响细胞结合的IgE的解离速率，也不诱导或抑制IgE的内化。mAb BD6不释放组胺。然而，它确实会导致细胞迅速铺展。到1小时时，细胞收缩成球形，表面覆盖着膜状刺突，并且很容易从组织培养板上脱落。这些变化与FcεRI激活后观察到的变化不同。mAb BD6从¹²⁵I表面标记的大鼠嗜碱性白血病细胞中免疫沉淀出一种由两种蛋白质组成的复合物，分子量分别为38至50 kDa和135 kDa，它们不是FcεRI的亚基。化学交联研究表明这些分子在细胞表面相互关联。通过免疫印迹法，mAb BD6与一种40 kDa的蛋白质发生反应。因此，mAb BD6与一种靠近FcεRI的表面蛋白结合，并在空间上抑制¹²⁵I-IgE的结合。
