ORIGINAL ARTICLESIdentification of human platelet glycoprotein VI-specific IgG autoantibody and its fragmentsChu, Xiaoxia; Hou, Ming; Peng, Jun; Zhu, Yuanyuan; Zhang, Feng; Ji, Xuebin; Wang, Lin; Ma, DaoxinAuthor Information Hematology Oncology Center, Qilu Hospital of Shandong University, Jinan, Shandong, People's Republic of China Received 27 November, 2005 Accepted 11 April, 2006 Correspondence and requests for reprints to Ming Hou, MD, PhD, Professor and Director, Hematology Oncology Center, Qilu Hospital of Shandong University, 107 West Wenhua Road, Jinan, Shandong 250012, People's Republic of China Tel: +86 531 82169879; fax: +86 531 86927544; e-mail: [email protected] Sponsorship: This study was supported by grants (numbers 30470742 and 30300312) to M.H. and J.P. from the National Natural Science Foundation of China, Beijing, China. Blood Coagulation & Fibrinolysis: July 2006 - Volume 17 - Issue 5 - p 403-407 doi: 10.1097/01.mbc.0000233371.26228.44 Buy Metrics Abstract Glycoprotein VI (GPVI), as a major receptor for collagen on the platelet surface, mediates the initial platelet contact with collagen, and causes platelet aggregation and thrombosis. Agents of anti-GPVI can inhibit the adhesion, activation and aggregation function of platelets, which can be used for preventing thrombotic diseases. To make humanized monoclonal antibodies by phage surface display technology, we studied plasmas from 44 patients with chronic idiopathic thrombocytopenic purpura using modified monoclonal antibody immobilization of platelet antigen assays. GPVI-specific antibodies were found in six (13.6%) patients. Among these, only one showed significant inhibition of platelet aggregation induced by collagen. The IgG antibody and F(ab′)2 fragments of this patient's plasma were further purified and their immunoreactivities and effects on platelet aggregation were reanalyzed. It was found that purified IgG and its F(ab′)2 fragments from the patient not only retained the ability to bind to platelet GPVI, but also inhibited collagen-induced platelet aggregation. In this study, therefore, the specific anti-platelet GPVI autoantibody that inhibits collagen-induced platelet aggregation has been successfully screened out, which can be used to develop completely humanized anti-GPVI phage antibody. © 2006 Lippincott Williams & Wilkins, Inc.