Characterization of a murine monoclonal antibody that mimics heparin-induced thrombocytopenia antibodies
Characterization of a murine monoclonal antibody that mimics heparin-induced thrombocytopenia antibodies
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DOI：
10.1182/blood.v95.5.1533.005k01_1533_1540
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发表时间：
2000-03-01
期刊：
影响因子：
20.3
通讯作者：
Poncz, M
中科院分区：
文献类型：
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作者：
Arepally, GM;Kamei, S;Poncz, M
几乎所有肝素诱导的血小板减少/血栓形成(HIT/HITT)患者和一些没有临床症状的接触肝素的人都可以检测到抗PF4/肝素抗体。抗PF4/肝素抗体在HIT/HITT发病机制中的作用一直难以确定，因为血清中发现的抗体通常是多克隆和多特异性的。为了解决这一问题，我们研制了一种抗人(H)PF4/肝素复合体的鼠源性单抗。鉴定了一种能与HPF4/肝素复合体特异性结合的单抗(命名为KKO)，KKO与HPF4/肝素复合体的最大结合率与HIT/HIT抗体的PF4与肝素的摩尔比相近。Kko还与HPF4结合，与其他糖胺聚糖结合。KKO激活的血小板需要肝素，并被FcγRIIA阻断，在有PF4存在的情况下，KKO与内皮细胞结合，但不能与缺乏硫酸肝素蛋白多糖的CHO细胞结合。KKO和HIT/HITT血清对与肝素络合的PF4变异体的识别效果一样好。KKO竞争与HIT/HITT抗体的子集结合，这些抗体相对不受PF4第三结构域突变的影响。KKO和RTO是一种不需要肝素结合的小鼠抗HPF4单抗，其核苷酸和预测的氨基酸序列在重链和轻链免疫球蛋白可变区都没有明显的关系。这些研究表明，KKO概括了一组HIT/HITT抗体的抗原和功能特异性，因此可能为了解受影响人群的血小板减少和血栓形成的发病机制提供线索。(C)2000年，由美国血液病学会提供。
Antibodies to PF4/heparin can be demonstrated in almost all patients with heparin-induced thrombocytopenia/thrombosis (HIT/HITT) and in some persons exposed to heparin who do not have clinical manifestations. The role of anti-PF4/heparin antibodies in the pathogenesis of HIT/HITT has been difficult to establish because the antibodies found in serum are generally polyclonal and polyspecific. To circumvent this problem, we developed a murine monoclonal antibody (mAb) to human (h) PF4/heparin complexes. A monoclonal IgG(2bK) antibody (designated KKO) was identified that bound specifically to hPF4/heparin complexes, Maximal binding of KKO to hPF4/heparin complexes occurred at similar molar ratios of PF4:heparin observed for HIT/HITT antibodies. KKO also bound to hPF4 in association with other glycosaminoglycans. Platelet activation by KKO required heparin and was abrogated by blockade of Fc gamma RIIA, In the presence of PF4, KKO bound to endothelial cells, but not to CHO cells lacking heparan sulfate proteoglycans. Variants of PF4 complexed to heparin were recognized equally well by KKO and HIT/HITT sera. KKO competes for binding with a subset of HIT/HITT antibodies that are relatively spared by mutations in the 3rd domain of PF4. The nucleotide and predicted amino acid sequences of KKO and RTO, a murine anti hPF4 mAb that does not require heparin for binding, revealed no obvious relationship in either the heavy-or the light-chain immunoglobulin variable regions. These studies suggest that KKO recapitulates the antigenic and functional specificity of a subset of HIT/HITT antibodies and may, therefore, provide insight into the pathogenesis of thrombocytopenia and thrombosis in affected persons. (C) 2000 by The American Society of Hematology.