Yano S, Suzuki K, Katoh M, Sugita Y, Kaku S, Kawamura K, Masuho Y
Molecular Medicine Research Laboratories, Yamanouchi Pharmaceutical Co., Ltd., Ibaraki.
J Biochem. 1994 Oct;116(4):778-86. doi: 10.1093/oxfordjournals.jbchem.a124596.
We have developed two monoclonal antibodies (MAbs), B6A3 and C4G1. The whole molecules of the two MAbs inhibited in vitro human platelet aggregation induced by either ADP, collagen or thrombin, and their F(ab')2 fragments inhibited ex vivo platelet aggregation induced by ADP in monkey. The concentrations necessary for complete inhibition were 5 and 1 microgram/ml for B6A3 and C4G1, respectively. The Fab fragment of C4G1 but not B6A3 inhibited platelet aggregation. B6A3 and C4G1 bound to activated platelets with dissociation constants of 0.25 and 0.82 nM, respectively. B6A3 recognized an epitope on beta 3, which was sensitive to reduction and alkylation of cystine residues, and C4G1 recognized a conformational epitope on the alpha IIb beta 3 complex, which was sensitive to EDTA. The binding of fibrinogen to activated platelets was inhibited by both MAbs. However, the binding of fibrinogen to isolated alpha IIb beta 3 was inhibited by the whole molecule of C4G1 but not B6A3, although both MAbs bound to the isolated alpha IIb beta 3. The binding of these MAbs to the isolated alpha IIb beta 3 was not inhibited by either Arg Gly Asp Ser (RGDS) or fibrinogen gamma-peptide. In addition, B6A3 but not C4G1 bound to human endothelial cells. These MAbs should contribute to the elucidation of the mechanism of platelet aggregation.
我们研发了两种单克隆抗体（MAbs），即B6A3和C4G1。这两种单克隆抗体的完整分子在体外可抑制由ADP、胶原蛋白或凝血酶诱导的人血小板聚集，其F(ab')2片段在体内可抑制由ADP诱导的猴血小板聚集。B6A3和C4G1完全抑制所需的浓度分别为5微克/毫升和1微克/毫升。C4G1的Fab片段而非B6A3可抑制血小板聚集。B6A3和C4G1与活化血小板结合，解离常数分别为0.25纳摩尔和0.82纳摩尔。B6A3识别β3上的一个表位，该表位对胱氨酸残基的还原和烷基化敏感，C4G1识别αIIbβ3复合物上的一个构象表位，该表位对EDTA敏感。两种单克隆抗体均抑制纤维蛋白原与活化血小板的结合。然而，尽管两种单克隆抗体均与分离的αIIbβ3结合，但C4G1的完整分子而非B6A3抑制纤维蛋白原与分离的αIIbβ3的结合。这些单克隆抗体与分离的αIIbβ3的结合不受精氨酸 - 甘氨酸 - 天冬氨酸 - 丝氨酸（RGDS）或纤维蛋白原γ肽的抑制。此外，B6A3而非C4G1与人内皮细胞结合。这些单克隆抗体应有助于阐明血小板聚集的机制。
