AUTOANTIBODIES AGAINST THE PLATELET GLYCOPROTEIN IIB/IIA COMPLEX IN PATIENTS WITH CHRONIC ITP

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  • 1 January 1984
    • journal article
    • research article
    • Vol. 63  (2) , 368-375
Abstract
Chronic idiopathic thrombocytopenic purpura (ITP) is caused by an antibody reactive with platelet-associated antigens. Some patients with chronic ITP have autoantibodies against the platelet glycoprotein (GP) IIb/IIIa complex. Microtiter wells, coated with a monoclonal antibody (2G12) specific for GPIIb/GPIIIa were reacted with GPIIb/GPIIIa contained in a platelet extract. Control wells containing the same antibody werer reacted with a cell extract containing no GPIIb/GPIIIa. After washing, the wells were reacted with patient or control plasma, and IgG binding was detected using 125I-Fab2-anti-human IgG. Assay values were expressed as binding ratios (cpm GPIIb/GPIIIa wells/cmp control wells). Plasma from 5 of 56 patients with chronic ITP had ratios (1.36-3.14) greater than 3 SD above the mean (.+-. SD) of control plasms.sbd.0.93 .+-. 0.12. Elevated values were also noted in 2 patients with anti-P1A1 antibody (ratios > 30) and in 1 patients with Hodgin''s disease and an ITP-like syndrome (ratio 1.53). Normal values were noted in 34 patients with a variety of immune and nonimmun diseases. Plasma from 2 of the positive ITP patients was reacted with 125I-surface-labeled platelets and, after solubilization, the IgG and bound antigen were precipitated with Staph-A. Autoradiographs from SDS-PAGE [sodium dodecyl sulfate-polyacrylamide gel electrophoresis] electrophoresis of the Staph-A-bound proteins shows 2 radioactive bands consistent in size with GPIIb and GPIIIa.

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