Immunoblot analysis of platelet glyeoprotein IIb in patients with Glanzmann thrombasthenia in Israel

Abstract

Recent studies have indicated that severe (''type I'') Glanzmann thrombasthenia is a heterogeneous hereditary disorder caused by quantitative and/or qualitative abnormalities of platelet membrane glycoproteins (GP) IIb and IIIa. Immunoblot analysis of sodium dodecyl sulphate (SDS)-solubilized platelets was carried out on controls and 18 patients (12 Iraqi-Jews, two Iranian Jews and four Arabs) employing three antibodies (one monoclonal and two polyclonal) directed at different sites on GPIIb. Nonreduced control platelet samples contained a major Mr .apprx. 140k immunoreactive protein that was split into an Mr .apprx. 120k (.alpha.) and an Mr .apprx. 25k (.beta.) band after reduction with mercaptoethanol. The nonreduced samples from all 18 patients tested had trace amounts of Mr .apprx. 140k band corresponding to normal GPIIb; the intensity of this band was estimated to be < 1% of the normal amount. Unlike the control samples, however, this Mr .apprx. 140k band did not change electrophoretic mobility following reduction. Since GPIIb originates from a single chain precursor molecule of Mr .apprx. 140k that comprises both the .alpha. and .beta. chains, and which does not change mobility with reduction, our data suggest that the platelets of these patients contain small amounts of this precursor.