Drug-induced thrombocytopenia: localization of the binding site of GPIX-specific quinine-dependent antibodies.

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Asvadi P, Ahmadi Z, Chong BH

Drug-induced thrombocytopenia: localization of the binding site of GPIX-specific quinine-dependent antibodies.

Blood. 2003 Sep 1;102(5):1670-7. Epub 2003 May 8.

PubMed ID

12738668 [ View in PubMed

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Abstract

Immune thrombocytopenia is a common complication of therapy with a large number of drugs. The most widely studied drug-induced immune thrombocytopenia (DIT) is caused by quinine. In most cases of DIT, antibodies bind to the platelet membrane glycoprotein (GP) Ib-IX complex in a drug-dependent fashion and bring about increased platelet clearance by the reticuloendothelial system resulting in thrombocytopenia. Here, we report the characterization of the quinine-dependent antibody activity of sera from 13 patients with quinine-induced thrombocytopenia. In our series of patients, GPIX was the most prevalent target of quinine-dependent antibodies. To identify the structural determinants of GPIX recognized by quinine-dependent antibodies, 4 chimeric mouse/human GPIX constructs and stable Chinese hamster ovary (CHO) cell lines that expressed the chimeras in association with GPIbalpha and GPIbbeta were produced. The analysis of 6 patient sera with the chimeric cell lines provided evidence for localization of the anti-GPIX quinine-dependent antibody binding site to the C-ext region (amino acid [aa] 64-135) of human GPIX. Further characterization of the C-ext region of the GPIX indicated that replacement of the Arg110 and Gln115 of the human GPIX with the corresponding residues from mouse (Gln and Glu, respectively) resulted in a significant reduction in the binding of GPIX antibodies in our series of patients, with Arg110Gln, giving a more pronounced effect than Gln115Glu. Hence, these 2 residues, particularly Arg110, play an important role in the structure of the antigenic site on GPIX recognized by anti-GPIX antibodies.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Quinine	Platelet glycoprotein IX	Protein	Humans	Unknown	Other	Details