QUANTITATION OF PLATELET-SPECIFIC AUTOANTIBODIES IN PLATELET ELUATES OF ITP PATIENTS MEASURED BY A NOVEL ELISA USING THE PURIFIED GLYCOPROTEIN COMPLEXES GPIIB IIIA AND GPIB/IX AS ANTIGENS/

Immune thrombocytopenic purpura (ITP) is a disorder caused by anti-pla telet autoantibodies (Ab), most of which are directed against epitopes on platelet membrane glycoprotein complexes GPIIb/IIIa and GPIb/IX. T o detect platelet Ab, reliable techniques, such as MAIPA or immunobead assay, have been developed. They all achieve their selective specific ity by the use of monoclonal antibodies (MoAb) against defined glycopr oteins of the platelet membrane. In order to determine the most freque nt Abspecificities, a novel enzyme-linked immunosorbent assay, named p latelet-glycoprotein-ELISA (P-GP-ELISA), has been developed. It uses p urified GPIIb/IIIa and GPIb/IX complexes, respectively, as antigens an d enables determination of platelet-associated as well as circulating Ab (IgG, IgM). MoAbs are not required and therefore there is no risk o f competition between MoAb and Ab, Levels of Ab in patients with the c linical diagnosis of an idiopathic thrombocytopenic purpura were analy sed. 92.7% (76/82) platelet eluates with significantly increased level s of Ab against at least one of the glycoproteins were found, whereas no sample from healthy volunteers (0/37) gave a positive result, point ing to a high sensitivity and specificity of the test system. Since it s application is also easy and quick, P-GP-ELISA should facilitate det ection of Ab against platelet membrane proteins in routine determinati ons.