一株抗人血小板第4因子单克隆抗体(SZ-95)的特异性鉴定

Study on epitope and function of a novel monoclonal antibody against platelet factor 4

目的 研究一株新制备的抗人血小板第４因子（ＰＦ４）单克隆抗体（ｍＡｂ）ＳＺ－９５的抗原表位和对ＰＦ４结合肝素功能的影响。 方法通过间接ＥＬＩＳＡ、Ｗｅｓｔｅｒｎ ｂｌｏｔ以及肝素－ＰＦ４复合物ＥＬＩＳＡ研究ＳＺ－９５所识别的抗原决定簇和其对ＰＦ４生物学功能的影响。 结果 这株特异性识别人ＰＦ４的ｍＡｂ不识别与ＰＦ４高度同源的β－血小板球蛋白（β－ＴＧ），以及包括ＰＦ４分子中部大部分β折叠的合成多肽（Ｐ３４－５８）。并且，抗体结合肝素－ＰＦ４复合物的数量随复合物中的肝素量增加而减少。结论我们推测ＳＺ－９５识别的抗原表位可能位于人ＰＦ４ Ｎ末端的可变区域或者Ｃ末端α螺旋。并且ｍＡｂ结合肝素－ＰＦ４复合物的肝素剂量依赖性改变，说明ＳＺ－９５识别的抗原表位与肝素与ＰＦ４的结合位点有关，可能影响ＰＦ４中和肝素的功能，有助于ＰＦ４结构和功能的进一步研究。

Aim To identify the epitope recognized by a novel monoclonal antibody SZ-95 against Platelet Factor 4(PF4) and to study its effect on PF4 binding to heparin. Methods The epitope of SZ-95 and its action on biological activities of PF4 was determined by indirect ELISA,Western blot and heparin-PF4 complex ELISA.Results The mAb SZ-95 recognizing human PF4 specifically does not react with beta-thromboglobulin(β-TG) and the synthetic peptide corresponding to amino acids 34 to 58 (P34-58). The number of SZ-95 binding to heparin-PF4 complex reduces along with the increment of heparin in complex. Conclusion It is suggested that the epitope of SZ-95 locate in the carboxylterminal α-helix or conformation flexible N-terminal region.The quantity of SZ-95 binding to heparin-PF4 complex dependent on the number of heparin in complex demonstrated that the epitope of SZ-95 is related to the binding site of PF4 on heparin.The effect of SZ-95 on PF4 binding to heparin provides evidence for further study fo structure and function of PF4.