Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065, United States.
Department of Pathology, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY 10461, United States.
Thromb Res. 2017 Aug;156:119-125. doi: 10.1016/j.thromres.2017.06.014. Epub 2017 Jun 9.
The antiphospholipid syndrome (APS) is marked by autoantibodies that recognize anionic phospholipids in a cofactor-dependent manner. A role for complement has been implicated in the pathophysiology, however, elevations of complement activation markers have not been consistently demonstrated in clinical studies. We therefore designed a proof-of-principle study to determine whether complement activation might be detectable in APS by first exposing plasmas to phospholipid vesicles.
We examined complement activation markers in patients with APS, non-APS thrombosis, systemic lupus erythematosus, cancer, patients with antiphospholipid antibodies without thrombosis (APL) and healthy controls. Direct measurements of plasma C5a and sC5b-9 levels were compared to levels that were generated in normal serum by phospholipid vesicles that had been pre-incubated with the same plasmas. We then determined the effects of the C5 inhibitor, eculizumab, examined the complement pathways involved, and determined whether the effects could be reproduced with purified IgGs and β2-glycoprotein I (β2GPI).
Plasma levels of C5a and sC5b-9 were higher, but not significantly increased in APS patients compared to healthy controls. In contrast, phospholipid vesicles pre-incubated with APS plasmas generated significantly higher levels than healthy controls and the other groups, except for APL patients. Complement activation was abrogated by addition of eculizumab. The results with substrate sera indicated that the alternative and classical/lectin pathways were involved. The results were reproducible with purified IgGs and β2GPI.
This proof-of-principle study confirms a role for complement in APS and opens the possibility of monitoring complement activation by including phospholipid vesicles in assay systems.
抗磷脂综合征（APS）的特征是自身抗体以依赖辅助因子的方式识别阴离子磷脂。补体在其病理生理学中发挥作用，然而，在临床研究中并未一致证明补体激活标志物的升高。因此，我们设计了一项原理验证研究，通过首先将血浆暴露于磷脂囊泡来确定 APS 中是否可以检测到补体激活。
我们检查了 APS、非 APS 血栓形成、系统性红斑狼疮、癌症、无血栓形成的抗磷脂抗体患者（APL）和健康对照者的补体激活标志物。将血浆 C5a 和 sC5b-9 水平的直接测量值与正常血清中预先孵育相同血浆的磷脂囊泡产生的水平进行比较。然后，我们确定了 C5 抑制剂依库珠单抗的作用，检查了涉及的补体途径，并确定是否可以使用纯化的 IgG 和β2-糖蛋白 I（β2GPI）来复制这些作用。
与健康对照组相比，APS 患者的血浆 C5a 和 sC5b-9 水平升高，但无统计学意义。相比之下，与健康对照组和其他组（除 APL 患者外）相比，预先用 APS 血浆孵育的磷脂囊泡产生的 C5a 和 sC5b-9 水平显著升高。加入依库珠单抗可阻断补体激活。底物血清的结果表明，替代途径和经典/凝集素途径均参与其中。使用纯化的 IgG 和β2GPI 可重复该结果。
这项原理验证研究证实了补体在 APS 中的作用，并通过在检测系统中包含磷脂囊泡，为监测补体激活提供了可能性。
