ANTIBODIES TO PLATELET GLYCOPROTEIN-V IN POLYTRANSFUSED PATIENTS WITH HEMATOLOGICAL DISEASE

Polytransfused patients often develop platelet-reactive antibodies (PRAb). These give positive reactions in the platelet immunofluorescence test (PIFT) and may be either lymphocytotoxic (LCTAb) or platelet-specific antibodies (PSAb). The latter may be detected in the PIFT using chloroquine-treated platelets (Chl-PIFT) or by immunoblotting. Serial samples from 106 multiply transfused patients with bone marrow failure were screened by PIFT using a microplate method and flow-cytometric analysis. PSAb activity was confirmed by Chl-PIFT. In 45 (42%) of the patients studied PSAb were detected; 37 (35%) formed LCTAb and 19 (51%) had co-existent PSAb. Sera from 25 of 27 patients with a positive Chl-PIFT, retested by immunoblotting, recognised determinants of Mr 82-160 kD on whole platelets. A large group became sensitised to a component of Mr 105-115 kD reduced (99 kD non-reduced) with similar electrophoretic mobility to GPIlIa using a monoclonal anti-GPIIIa and two human polyclonal anti-HPA-1a sera; some also produced anti-GPIIb. The largest group recognised a determinant of Mr 80-83 kD, probably glycoprotein V (GPV). Three sera were immunoblotted against thrombin-treated platelets and the results confirmed GPV specificity.