Molecular Characterization of Quinine/Quinidine Drug-Dependent Antibody Platelet Interaction Using Monoclonal Antibodies

• Published in: Blood Vol. 66; no. 6; pp. 1292 - 1301
• Main Authors: Berndt, Michael C., Chong, Beng H., Bull, Helen A., Zola, Heddy, Castaldi, Peter A.
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 01-12-1985; The Americain Society of Hematology
• Subjects: Antibodies, Monoclonal - immunology; Antigen-Antibody Reactions - drug effects; Binding Sites, Antibody; Biological and medical sciences; Blood Platelets - immunology; Blood Platelets - metabolism; Drug toxicity and drugs side effects treatment; Fluorescent Antibody Technique; Glycoproteins - isolation & purification; Humans; Medical sciences; Peptide Hydrolases - pharmacology; Pharmacology. Drug treatments; Platelet Aggregation; Quinidine - pharmacology; Quinine - pharmacology; Toxicity: blood; Platelet; Monoclonal antibody; Mechanism of action; Antibody; Quinine; Interaction
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V66.6.1292.1292

Two murine monoclonal antibodies, FMC 25 and AN 51, directed against distinct epitopes on the glycoprotein lb complex, have been used to further define the mechanism of quinine/quinidine drug-dependent antibody interaction with platelets. FMC 25, directed against an epitope on glycoprotein IX, had no effect on platelet aggregation induced by collagen or adenosine diphosphate and little, if any, effect on ristocetin-induced platelet agglutination. FMC 25 and its (Fab)2 fragment, however, were potent inhibitors of drug-dependent antibody-induced platelet aggregation and blocked binding of drug-dependent antibody to platelets as assessed by indirect platelet immunofluorescence. In contrast, AN 51, directed against an epitope on the α-subunit of glycoprotein lb, blocked ristocetin-induced, factor VIII/von Willebrand factor (FVIII/vWF)-dependent platelet agglutination but not drug-dependent antibody-induced platelet aggregation or binding of drug-dependent antibody to platelets. Selective proteolytic removal of the majority of the α-subunit of glycoprotein lb (glycocalicin) from platelets by treatment with calcium-dependent protease did not affect binding of drug-dependent antibody. In addition, a quinidine-dependent antiplatelet antibody immunoprecipitated glycoprotein lb complex from normal platelets and the membrane-associated proteolytic remnant of the glycoprotein lb complex from calcium-dependent protease-treated platelets. Preincubation of drug-dependent antibody with purified glycoprotein lb complex inhibited subsequent binding of antibody to platelets, but the separated components, glycoprotein lb and glycoprotein IX, were both ineffective, suggesting that the normal interaction between glycoprotein lb and glycoprotein IX in the intact complex was necessary for drug-dependent antibody recognition. The functional response of platelets to drug-dependent antibody was not mediated by way of platelet Fc receptor, since aggregation of washed platelets by acetone-aggregated IgG was not inhibited by FMC 25 (Fab)2. FVIII/vWF was not required for drug-dependent antibody-induced platelet aggregation. The combined evidence is consistent with quinine/quinidine-dependent antibody-platelet interaction occurring by way of a FVIII/vWF-independent, Fc receptor-independent mechanism that probably involves binding of antibody to glycoprotein IX or the β-subunit of glycoprotein lb or both.
© 1985 by Grune & Stratton, Inc.