The platelet alloantigen Zwa or PlA1 is expressed by cultured endothelial cells.

Recently, the synthesis by cultured human endothelial cells of a membrane protein complex immunologically related to platelet glycoprotein (GP) IIb/IIIa complex was demonstrated. Since platelet GP IIIa is known to carry the platelet alloantigen Zwa or PlA1, studies were performed to establish whether this antigen is also expressed on endothelial cells. The present report describes the results of these studies, which provide evidence for the presence of the Zwa or PlA1 antigen on the surface of cultured human endothelial cells.

Cultured human endothelial cells synthesize a plasma membrane protein complex immunologically related to the platelet glycoprotein IIb/IIIa complex.

We have previously demonstrated that endothelial cells synthesize a plasma membrane protein indistinguishable from platelet glycoprotein (GP) IIa. The present study provides evidence for a further analogy between the platelet and the endothelial cell membrane by showing that cultured endothelial cells also synthesize a membrane protein complex immunologically related to the platelet GP IIb/GP IIIa complex. This evidence is based on the following observations: (1) C17, a murine monoclonal antiplatelet GP IIIa antibody, consistently precipitates two proteins, apparent molecular weights, respectively, 115,000 and 125,000 reduced and 95,000 and 135,000 nonreduced, from metabolically (35S-methionine) as well as surface 125I-labeled cultured human endothelial cells; (2) upon crossed immunoelectrophoresis of solubilized endothelial cells against a polyclonal rabbit antiplatelet antiserum and 125I-labeled C17 IgG, a single precipitate of the protein(s) recognized by C17 is observed.

Vascular endothelial cells synthesize a plasma membrane protein indistinguishable from the platelet membrane glycoprotein IIa.

To define the role of membrane components that function in endothelial cell physiology and to characterize them biochemically, we have attempted to prepare monoclonal antibodies specific for endothelial cells. Several clones were obtained producing antibodies which bound to endothelial cells and also to platelets. The antibody of one of these clones, CLB-HEC 75, was studied in more detail.