Immunobiology of GPIIb/IIIa

纤维蛋白原受体拮抗剂（FRA）是一类很有前途的新型抗血栓药物。然而，在迄今为止进行的这些药物的临床试验中，0.1-1.0%的治疗患者发生了急性重度血小板减少症。虽然临床表现提示免疫学病因，但关于这一点的已发表信息很少。在初步研究中，我们已经获得了FRA诱导的血小板减少症是由抗体（abs）引起的证据，这些抗体通常是“天然存在的”，它们识别用FRA处理的血小板上的GPIIb/IIIa。在本申请中，我们提出研究来表征这种疾病的发病机制，探索负责任的“天然”抗体的意义，并开发改进的诊断方法和识别有风险发展这种并发症的患者。发病机制-与FRA诱导的血小板减少症相关的Ab将重点描述以下假设：1）在接受阿昔单抗（ReoPro）治疗的患者中引起血小板减少症的Ab对嵌合阿昔单抗分子中的C末端（人）肽序列和/或鼠序列具有特异性，2）在接受配体模拟化合物治疗的患者中，Ab识别BPII/IIIA上的配体结合位点（LIBS）。我们将寻求开发一种由配体模拟FRA诱导的血小板减少症的小鼠模型，在该模型中可以系统地研究FRA诱导的血小板减少症的机制和负责任的ABS的起源。所获得的信息将用于开发敏感、特异和实用的方法，以识别能够引起FRA治疗患者血小板减少的abs，并预测FRA是否可以安全给药。“天然抗体”（NA）-NA涉及正常的身体稳态和各种免疫疾病。我们建议探讨的假设，一些相对常见的NA识别配体诱导的构象变化的GPIIb/IIIa异源二聚体，这些NA的特点，以FRA诱导的血小板减少症的关系，并确定其免疫起源，其在血小板中的潜在作用和它们的影响，血小板质量储存前输血。B细胞库-我们将利用免疫球蛋白V基因扩增和噬菌体展示技术来定义患者和正常受试者使用的B细胞库，以产生对配体占据的GPIIb/IIIa特异性的abs，并在分子水平上表征NA和病理性抗体之间的关系。

Fibrinogen receptor antagonists (FRAs) are a promising new family of anti-thrombotic drugs. However, in clinical trial of these agents conducted to date, 0.1-1.0% of treated patients has experienced acute, severe thrombocytopenia. Although clinical presentation suggests an immunologic etiology, very little published information on this point is available. In preliminary studies, we have obtained evidence that FRA- induced thrombocytopenia is caused by antibodies (abs), often "naturally occurring", that recognize GPIIb/IIIa on platelets treated with an FRA. In this application, we propose studies to characterize the pathogenesis of this disorder, explore the significance of the responsible "natural" antibodies, and develop improved methods for diagnosis and for identifying patients at risk to develop this complication. Pathogenesis-Abs associated with FRA-induced thrombocytopenia will be characterized with emphasis on the following hypotheses: 1) Abs that cause thrombocytopenia in patients treated with abciximab (ReoPro) are specific for C terminal (human) peptide sequences and/or murine sequences in the chimeric abciximab molecule and 2) Abs in patients treated with ligand-mimetic compounds recognized ligand-binding sites (LIBS) on BPII/IIIA. We will seek to develop a murine model of thrombocytopenia induced by ligand-mimetic FRAs in which mechanisms of FRA-induced thrombocytopenia and the origin of the responsible abs can be systematically studied. Information gained will be used to develop sensitive, specific and practical methods for identifying abs capable of causing thrombocytopenia in FRA-treated patients and for predicting whether an FRA can be safely administered. "Natural Antibodies" (NA)-NA have been implicated in normal body homeostasis and in various immune disorders. We propose to explore the hypothesis that some relative common NA recognize ligand-induced conformation changes in the GPIIb/IIIa heterodimer, to characterize the relationship of these NA to FRA-induced thrombocytopenia, and to define their immunologic origin, their potential role in platelet and their effects on the quality of platelets stored prior to transfusion. B cell repertoire- We will utilize immunoglobin V gene amplification and phage display technology to define the B cell repertoire utilized by patients and normal subjects to generate abs specific for ligand-occupied GPIIb/IIIa and to characterize the relationship between NA and pathologic antibodies at a molecular level.