POSSIBLE ORIENTATIONAL CONSTRAINTS DETERMINE SECRETORY SIGNALS INDUCED BY AGGREGATION OF IGE RECEPTORS ON MAST-CELLS
POSSIBLE ORIENTATIONAL CONSTRAINTS DETERMINE SECRETORY SIGNALS INDUCED BY AGGREGATION OF IGE RECEPTORS ON MAST-CELLS
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DOI：
10.1002/j.1460-2075.1988.tb03304.x
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发表时间：
1988-12-20
期刊：
影响因子：
11.4
通讯作者：
PECHT, I
中科院分区：
文献类型：
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作者：
ORTEGA, E;SCHWEITZERSTENNER, R;PECHT, I
在分析RBL-2 H3系的肥大细胞对它们的Fc ε R的交联的分泌应答中，使用了对IgE的单价高亲和力膜受体（Fc ε R）特异的三种生物活性单克隆抗体（mAb）。所有三种mAb（命名为F4、H10和J17）彼此完整，并与IgE完整以结合F ε R。它们的结合化学计量为1 Fab：1 Fc.R，因此，完整的mAb可使Fc. R. R仅聚集成二聚体。由于所有三种mAb均诱导分泌，因此我们得出结论，Fc γ R二聚体构成了RBL-2 H3细胞分泌介质的足够的“信号元件”。然而，细胞对这三种mAbs的分泌剂量反应明显不同：F4引起相当高的分泌，几乎达到细胞含量的80%。通过分析Fab片段和完整mABS的结合数据，推导出受体二聚化的内在亲和力和平衡常数。这些参数用于计算由每种抗体引起的Fc γ R二聚化的程度。然而，对三种mAb的不同分泌应答不能简单地根据Fc. γ. R的程度来合理化，Fc. γ.R不仅是决定引起分泌的信号的大小的交联Fc. γ.R的数量，而且由每种单独的mAb施加的其他限制也是重要的。这些约束最有可能是限制性的，在所产生的二聚体中产生不同取向的Fc.这些结果提供，据我们所知，第一个证据的相对取向的受体交联在刺激聚集过程中可能发挥的作用。
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) complete with each other and with IgE for binding to the F.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, 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 fo 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 is not only the number of crosslinked Fc.epsilon.R which determines the magnitude of secretion-causing signal, but rather other constraints imposed by each individual mAb are also important. These constraints are most probably configruational ones, yielding differently oriented Fc.epsilon.Rs in the produced dimers. These results provide, to our knowledge, the first evidence for a possible role of the relative orientation of receptors being crosslinked in a stimulatory aggregation process.