NORMAL SYNTHESIS AND EXPRESSION OF ENDOTHELIAL GP IIb/IIIa IN GLANZMANN'S THROMBASTENIA

In Glanzmann’s thrombastenia (GT), an autosomal recessive inherited hemorrhagic disease, the platelet membrane glycoprotein (GP) IIb/IIIa complex is absent or reduced. Recently we and others demonstrated that cultured human umbilical vein endothelial cells synthesize a membrane protein complex that is structurally closely related to GP IIb/IIIa. Endothelial cells of thrombasthénie patients could, therefore be deficient in GP IIb/IIIa. We had the opportunity to culture endothelial cells isolated from the umbilical cord of a newborn with GT and to examine the plasma membrane composition of these cells. Employing a variety of immunochemical techniques, including immunoprecipitation, immunofluorescence staining and crossed immunoelectrophoresis, we demonstrated that the endothelial cells of the patient were indistinguishable from normal endothelial cells in their ability to synthesize and express GP IIb/IIIa. Our results indicate that GT is not accompanied by and "endotheliopathy".

Zw^a (P1^A1) is an alloantigen, located on platelet GP IIIa, and, consequently, Zw^a is absent on GT platelet. Data will he presented which show that not only normal endothelial IIIa carries the Zw^a antigen, hut also GT endothelial cells normally express Zw^a. This finding supports our view that GT endothelial GP IIb/IIIa is indistinguishable from normal endothelial GP IIb/IIIa. Moreover, this finding directly shows that the thrombastenic glycoprotein abnormality and the inheritance of Zw^a antigen are controlled by different genes.