Autoantibodies against platelet glycoprotein Ib/IX: a frequent finding in autoimmune thrombocytopenic purpura.
Many autoantibodies involved in the pathogenesis of autoimmune thrombocytopenic purpura (AITP) are directed against epitopes on platelet glycoproteins (GP). These autoantibodies are a specific diagnostic characteristic of patients with AITP. In this study, the relative frequency of antibodies against GPs IIb/IIIa and Ib/IX was assessed in sera from 81 AITP patients with a glycoprotein-specific enzyme immunoassay (MAIPA assay) using monoclonal antibodies against these platelet GPs. All sera contained platelet-specific antibodies which had been detected by platelet immunofluorescence. Of the 81 antibodies tested, 58 (72%) reacted with at least one of the platelet GPs studied. Autoantibodies against GPIb/IX were as common as antibodies against the GPIIb/IIIa complex. The same ratio of specificities was observed on autologous platelets of an independent cohort of 29 patients. The epitope of three autoantibodies against GPIb/IX and of mab Gi10, a monoclonal antibody, which inhibits binding of these autoantibodies, was further characterized. Severity of thrombocytopenia was not related to the GP specificity of the autoantibody. The observation that in 23 (28%) of these sera the antigenic determinants could not be assigned to the glycoproteins under investigation suggests that platelet autoantibodies may react with other GPs or other membrane constituents, e.g. glycolipids.
Kiefel
V
V
Institute of Clinical Immunology and Transfusion Medicine, Justus Liebig University, Giessen, Germany.
Santoso
S
S
Kaufmann
E
E
Mueller-Eckhardt
C
C
D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity / Q000276:immunology; D000937:Antigen-Antibody Reactions / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology*; D000939:Epitopes / Q000276:immunology; D006801:Humans; D010980:Platelet Membrane Glycoproteins / Q000276:immunology*; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000276:immunology*
D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D000939:Epitopes; D010980:Platelet Membrane Glycoproteins