ROLE OF KALLIKREIN-KININ SYSTEM IN MAINTENANCE OF PREGNANCY

凝血因子XII、前激肽释放酶和高分子量激肽原被称为激肽释放酶-激肽系统的蛋白质。最近，据报道，RPL患者中因子XII缺乏症的患病率惊人地高。我们现在已经测试了来自RPL患者的血浆样本中是否存在针对因子XII的自身抗体。对191例RPL患者进行因子XII活性筛查。我们发现34例（17.8%）患者存在因子XII缺乏（活性<60%）。这34例患者中有13例（38.2%）抗磷脂抗体阳性。我们假设因子XII缺乏可能部分是由于因子XII抗体的存在，并通过免疫印迹和ELISA检测因子XII缺乏患者的血浆样本中因子XII抗体的存在。我们发现，53.5%的RPL因子XII缺乏患者IgG抗因子XII抗体阳性（p<0.001，OR 36.8）。抗因子XII抗体识别因子XII的氨基末端重链区。文献报道，人因子XII通过氨基末端重链区与糖蛋白Ib-IX-V复合物结合抑制Thorombin诱导的血小板聚集。我们假设因子XII自身抗体可能与RPL相关。

Coagulation factor XII, prekallikrein and high molecular weight kininogen are known as proteins of kallikrein-kinin system. Recently, surprisingly high prevalence of factor XII deficiency among patients with RPL have been reported. We have now tested plasma samples from RPL patients for the presence of autoantibodies to factor XII. One hundred ninety one patients with RPL were screened for factor XII activity. We found 34 (17.8%) patients with factor XII deficiency (activity <60%). Thirteen (38.2%) of these 34 patients were positive for antiphospholipid antibodies. We hypothesized that factor XII deficiency may be partly due to presence of antibodies to factor XII and tested plasma samples from patients with factor XII deficiency for the presence of antibodies to factor XII by immunoblot and ELISA. We found that 53.5% of factor XII deficient patients with RPL were positive for IgG anti-factor XII antibodies (p<0.001, OR36.8). Anti-factor XII antibodies recognized the amino-terminal heavy chain region of factor XII. Literatures have reported that human factor XII binding to the glycoprotein Ib-IX-V complex via the amino-terminal heavy chain region inhibits thorombin-induced platelet aggregation. We hypothesize that autoantibodies to factor XII may be associated with RPL.