Identification of antigen for cause of ITP by the new molecular biological method (SEREX)

为明确特发性血小板减少性紫癜（ITP）特异性抗原的病因，采用高灵敏度基因克隆方法直接分析ITP特异性抗原基因，采用重组表达克隆方法（SEREX）进行抗原血清学鉴定。我们从UT-7/血小板生成素中提取RNA并制备cDNA。将该cDNA在大肠杆菌中表达后，获得38个与ITP患者血清反应的克隆。其中9个克隆为未知克隆，19个克隆为已知克隆。我们重点研究人丁型肝炎抗原相互作用蛋白A（dip A），因为它对ITP血清有强烈反应。用RT-PCR方法检测dip A在所有细胞系中的表达。用免疫印迹法检测ITP患者血清中抗dip A抗体。60%的ITP患者dip A抗体阳性，而健康志愿者仅20%阳性。dip-A基因点突变的可能性及抗dip-A抗体在ITP发病中的作用有待进一步研究。

To identify the cause of specific antigen in idiopathic thrombocytopenic purpura (ITP), we directly analyzed the gene of specific antigen in ITP by high sensitivity of genetic cloning method ; serological identification of antigens by recombinant expression cloning (SEREX). We extracted the RNA from UT-7/thrombopoietin and made the cDNA. After expression of protein from the cDNA in E-Coli, 38 clones which were reacted to the serum of patients with ITP were obtained. Out of them, 9 clones were unknown and 19 were known by the analysis of sequence of gene. We focused human hepatitis delta antigen interacting protein A (dip A), because it strongly reacted to the ITP serum. By RT-PCR method, we detected the expression of dip A in all cell line. We examined the anti-dip A antibody in patients with ITP by western blot method. Sixty percent of ITP patients were positive for dip A antibody, but only 20% of healthy volunteers were positive. The possibility of point mutation in dip-A and role of anti-dip-A antibody in the onset of ITP should be studied furthermore.