Endothelial cells synthesize a heterodimeric adhesion molecule, the vitronectin receptor (VnR), which is similar to the platelet glycoprotein (GP)IIb/IIIa complex. The subunits of the endothelial VnR (VnR alpha and GPIIIa) have been studied for their ability to express alloantigens associated with platelet GPIIb and IIIa. We previously showed that endothelial GPIIIa can express the platelet all...

Recent studies have shown that antibodies characteristic of quinine- and quinidine-induced thrombocytopenia sometimes recognize the platelet membrane glycoprotein (GP) complex IIb/IIIa in addition to their well known target, GPIb/IX. We have investigated the frequency with which drug-induced antibodies bind to GPIIb/IIIa and the nature of their target epitopes. In studies of sera from 13 patien...

The platelet membrane glycoprotein (GP) IIb/IIIa complex, a member of the integrin family of adhesive receptors involved in cell-cell and cell-matrix interactions, contains binding sites for fibrinogen, von Willebrand factor, fibronectin, and vitronectin. Absence or defects of this receptor result in the platelet bleeding disorder Glanzmann's thrombasthenia. In this report, we describe the isol...

A murine monoclonal antibody specific for glycoprotein (GP)llla was prepared by immunization with a GPIIband GPIIla-enriched Triton X-1 14 extract of platelet membranes. This antibody, designated AP-3, was shown by indirect immunoprecipitation to react solely with GPIIIa derived from either P1 Alpositive or -negative individuals. The epitope on GPIIIa recognized by AP-3 is expressed on dissocia...

Neonatal alloimmune thrombocytopenic purpura associated with a new platelet-specific alloantigen Pena has been reported. We now provide direct evidence that the Pena determinant is associated with glycoprotein (GP) IIIa, but that it is distinct from epitopes that define the PlA system. By ELISA wherein monoclonal antibodies specific for GPIIb (Tab) and specific for GPIIIa (AP3) were used to cap...

Chronic thrombocytopenia is a common hematologic disorder in patients infected with the human immunodeficiency virus (HIV). Although often asymptomatic, the thrombocytopenia may be associated with a variety of bleeding abnormalities. Antigenic homology between HIV-1 gp120 and human platelet glycoprotein GPIIIa was reported. Here, the author performed a study to assess the structural homology be...

Drug-induced immune thrombocytopenia is caused by drug-dependent antibodies (DDAbs) that bind tightly to platelet glycoproteins only when drug is present. How drugs mediate this interaction is not yet resolved. Several studies indicate that sites recognized by DDAbs tend to cluster in specific structural domains, suggesting they may recognize a limited number of distinct epitopes. To address th...

Platelet membrane GPIIb is comprised of a disulfide-linked heavy chain (GPIIb(H)) and light chain (GPIIb(L)). We have examined the role of the two chains of GPIIb in the maintenance of the GPIIb-IIIa heterodimer and Arg-Gly-Asp (RGD) peptide-binding function. Lysates of surface radioiodinated platelets were treated with 1% 2-mercaptoethanol for 18 hours at 4 degrees C. Reduction of the intercha...

Drug-induced immune thrombocytopenia is caused by drug-dependent antibodies (DDAbs) that bind tightly to platelet glycoproteins only when drug is present. How drugs mediate this interaction is not yet resolved. Several studies indicate that sites recognized by DDAbs tend to cluster in specific structural domains, suggesting they may recognize a limited number of distinct epitopes. To address th...

A new platelet alloantigen, termed CA, has recently been implicated in a case of neonatal alloimmune thrombocytopenia (NATP) in a Filipino family in Canada. Maternal anti-CA serum reacted with glycoprotein (GP) IIIa and maintained its reactivity after removal of high mannose carbohydrate residues from GPIIIa. The monoclonal antibody (MoAb) AP3 partially blocked binding of anti-CA to GPIIIa, sug...