Ortega E, Schweitzer-Stenner R, Pecht I
Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
EMBO J. 1988 Dec 20;7(13):4101-9. doi: 10.1002/j.1460-2075.1988.tb03304.x.
Three biologically active monoclonal antibodies (mAbs) specific for the monovalent, high-affinity membrane receptor for IgE (Fc epsilon R) were employed in analysing the secretory response of mast cells of the RBL-2H3 line to crosslinking of their Fc epsilon R. All three mAbs (designated F4, H10 and J17) compete with each other and with IgE for binding to the Fc epsilon R. Their stoichiometry of binding is 1 Fab:1 Fc epsilon R, hence, the intact mAbs can aggregate the Fc epsilon Rs to dimers only. Since all three mAbs induce secretion, we conclude that Fc epsilon R dimers constitute a sufficient 'signal element' for secretion of mediators for RBL-2H3 cells. The secretory dose-response of the cells to these three mAbs are, however, markedly different: F4 caused rather high secretion, reaching almost 80% of the cells' content, while J17 and H10 induced release of only 30-40% mediators content. Both the intrinsic affinities and equilibrium constants for the receptor dimerization were derived from analysis of binding data of the Fab fragments and intact mAbs. These parameters were used to compute the extent of Fc epsilon R dimerization caused by each of the antibodies. However, the different secretory responses to the three mAbs could not be rationalized simply in terms of the extent of Fc epsilon R dimerization which they produce. This suggests that it is not only the number of crosslinked Fc epsilon Rs which determines the magnitude of secretion-causing signal, but rather other constraints imposed by each individual mAb are also important.(ABSTRACT TRUNCATED AT 250 WORDS)
三种针对IgE单价高亲和力膜受体（FcεR）的具有生物活性的单克隆抗体（mAb）被用于分析RBL-2H3系肥大细胞的FcεR交联后的分泌反应。所有这三种单克隆抗体（分别命名为F4、H10和J17）彼此之间以及与IgE竞争结合FcεR。它们的结合化学计量比为1个Fab：1个FcεR，因此，完整的单克隆抗体只能将FcεR聚集为二聚体。由于所有这三种单克隆抗体均能诱导分泌，我们得出结论，FcεR二聚体构成了RBL-2H3细胞分泌介质的足够“信号元件”。然而，细胞对这三种单克隆抗体的分泌剂量反应明显不同：F4引起相当高的分泌，几乎达到细胞内容物的80%，而J17和H10仅诱导30%-40%的介质释放。受体二聚化的内在亲和力和平衡常数均来自对Fab片段和完整单克隆抗体结合数据的分析。这些参数用于计算每种抗体引起的FcεR二聚化程度。然而，对这三种单克隆抗体不同的分泌反应不能简单地根据它们产生的FcεR二聚化程度来解释。这表明，不仅交联的FcεR数量决定了引起分泌信号的大小，而且每种单克隆抗体施加的其他限制也很重要。（摘要截短于250字）
