title: Platelet-associated anti-glycoprotein (GP) IIb-IIIa autoantibodies in chronic immune thrombocytopenic purpura mainly recognize cation-dependent conformations: comparison with the epitopes of serum autoantibodies.
abstract: Platelet-associated and serum anti-glycoprotein (GP) IIb-IIIa autoantibodies were investigated in 57 patients with chronic immune thrombocytopenic purpura (ITP). In modified antigen capture ELISA (MACE) using GPIIb-IIIa-specific-, GPIIb-specific-, and GPIIIa-specific-monoclonal antibody (mAb) for antigen capture, platelet-associated anti-GPIIb-IIIa antibodies were detected in 14 out of 37 patients (38%), and these antibodies could be detected with all 3 mAbs used for antigen capture. In the MACE using EDTA-treated platelets at 37 degrees C, the reactivity of platelet-associated anti-GPIIb-IIIa antibodies in 9 out of 10 patients was markedly reduced in both cases of GPIIb-specific- and GPIIIa-specific-mAb used. Immunoprecipitation experiments further confirmed that the EDTA-treatment abrogated the antigenicity of GPIIb-IIIa for platelet-associated antibodies in 2 patients. Serum anti-GPIIb-IIIa autoantibodies were detected in 23 out of 57 patients (40%). However, only 7 out of 23 serum anti-GPIIb-IIIa antibodies could be detected with all 3 mAbs. The MACE using EDTA-treated platelets further showed that the features of serum anti-GPIIb-IIIa antibodies were different from those of platelet-associated antibodies even in the same patient. Our data demonstrate that the platelet-associated anti-GPIIb-IIIa antibodies mainly recognize the cation-dependent antigenic determinants on GPIIb-IIIa and that serum anti-GPIIb-IIIa antibodies may contain some components which differ in specificity from platelet-associated antibodies.
authors.affiliation: Second Department of Internal Medicine, Osaka University Medical School, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kosugi
authors.forename: Y
authors.initials: Y
authors.lastname: Tomiyama
authors.forename: M
authors.initials: M
authors.lastname: Shiraga
authors.forename: H
authors.initials: H
authors.lastname: Kashiwagi
authors.forename: H
authors.initials: H
authors.lastname: Mizutani
authors.forename: Y
authors.initials: Y
authors.lastname: Kanakura
authors.forename: Y
authors.initials: Y
authors.lastname: Kurata
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuzawa
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology*; D001327:Autoimmune Diseases / Q000276:immunology*; D001792:Blood Platelets / Q000276:immunology; D002118:Calcium / Q000502:physiology*; D004492:Edetic Acid / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000737:chemistry* / Q000276:immunology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D046911:Macromolecular Substances; D008297:Male; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000737:chemistry* / Q000276:immunology*; D011487:Protein Conformation; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D000939:Epitopes; D007074:Immunoglobulin G; D046911:Macromolecular Substances; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D004492:Edetic Acid; D002118:Calcium