Beumer S, Heijnen H F, IJsseldijk M J, Orlando E, de Groot P G, Sixma J J
Department of Haematology, University Hospital Utrecht, The Netherlands.
Blood. 1995 Nov 1;86(9):3452-60.
We describe glycoprotein (GP) Ib as a mediator of adhesion to fibronectin, specifically in flow. A monoclonal antibody (MoAb) directed to the von Willebrand factor (vWF)-binding site on this receptor or the absence of this receptor on the platelet membrane, in the case of a patient with the Bernard-Soulier syndrome, reduced platelet coverage to fibronectin to approximately 30% of the control value. A MoAb directed to the GP Ib-binding site on vWF showed a similar effect. With washed platelets in the absence of plasma vWF, the inhibitory effect of the anti-GP Ib antibody was the same as with whole blood. No inhibition with the anti-GP Ib antibody was observed when we used blood from patients with severe von Willebrand disease (vWD) or from a patient with vWD type I (platelet low). Addition of vWF to vWD blood resulted in restoration of adhesion. Immunoelectron microscopy on platelets adhering to fibronectin showed that GP Ib was homogeneously distributed over the entire surface of the platelet. vWF was present at the central zone and the edges of the platelet and at the basal interface between the platelet and the fibronectin surface. No direct binding of vWF to fibronectin could be demonstrated. These data indicate that GP Ib-mediated adhesion to fibronectin fully depends on vWF and that normal levels of plasma or platelet vWF are sufficient for optimal adhesion to fibronectin. The data suggest that the presence of platelets during perfusion is a prerequisite for vWF to support platelet adhesion to fibronectin.
我们将糖蛋白（GP）Ib描述为血小板与纤连蛋白黏附的介质，特别是在血流中。针对该受体上血管性血友病因子（vWF）结合位点的单克隆抗体（MoAb），或者在患有伯纳德-索利尔综合征的患者中，血小板膜上缺乏该受体，会使血小板与纤连蛋白的结合率降低至对照值的约30%。针对vWF上GP Ib结合位点的MoAb也显示出类似的效果。在没有血浆vWF的情况下使用洗涤后的血小板，抗GP Ib抗体的抑制作用与全血中的相同。当我们使用重度血管性血友病（vWD）患者或I型vWD患者（血小板减少）的血液时，未观察到抗GP Ib抗体的抑制作用。向vWD血液中添加vWF可恢复黏附。对黏附于纤连蛋白的血小板进行免疫电子显微镜观察显示，GP Ib均匀分布在血小板的整个表面。vWF存在于血小板的中央区域和边缘以及血小板与纤连蛋白表面之间的基底界面处。未证明vWF与纤连蛋白有直接结合。这些数据表明，GP Ib介导的与纤连蛋白的黏附完全依赖于vWF，并且血浆或血小板vWF的正常水平足以实现与纤连蛋白的最佳黏附。数据表明，灌注过程中血小板的存在是vWF支持血小板与纤连蛋白黏附的先决条件。
