Galli M, Bevers E M, Comfurius P, Barbui T, Zwaal R F
Department of Haematology, Ospedali Riuniti, Bergamo, Italy.
Br J Haematol. 1993 Mar;83(3):466-72. doi: 10.1111/j.1365-2141.1993.tb04672.x.
We have recently described the in vitro mechanism of action of anticardiolipin (aCL) and lupus anticoagulant (LA) antibodies in patients with the antiphospholipid syndrome. LA antibodies inhibit coagulation reactions in plasma because they appear to recognize the complex of lipid-bound (human) prothrombin, whereas aCL antibodies require beta 2-glycoprotein I (beta 2-GPI) for binding to anionic phospholipids. aCL antibodies can be divided into two subgroups, according to their behaviour in lipid-dependent coagulation reactions: aCL-type A enhances the anti-coagulant effect of beta 2-GPI, whereas aCL-type B does not. In the present study we investigated the effect of purified aCL-type A and B and of LA antibodies on the procoagulant activity of both Ca-ionophore activated platelets and platelet-derived microvesicles, using an assay system with highly purified bovine coagulation factors Xa, Va, and prothrombin from human and bovine origin. In the absence of beta 2-GPI neither type of aCL was able to inhibit the prothrombinase activity of platelets or microvesicles. However, a strong and dose-dependent inhibition of the prothrombinase activity of both platelets and platelet-derived microvesicles was observed within a few minutes, when aCL-type A antibodies were added in combination with beta 2-GPI. This inhibitory effect was dependent also on the concentration of beta 2-GPI. Conversely, no inhibitory effect of aCL-type B antibodies on platelet- (or microvesicle) prothrombinase activity in the presence of beta 2-GPI could be observed. LA antibodies were able to inhibit in a dose-dependent way the procoagulant activity of activated platelets and platelet-derived microvesicles. With two LA preparations this inhibition was only apparent when human prothrombin was used as substrate, while a third preparation exhibited its inhibitory effect both in the presence of human and bovine prothrombin. The data indicate that, in the presence of their respective cofactors beta 2-GPI and prothrombin, aCL and LA antibodies interact with the membrane of activated platelets and platelet-derived microvesicles in a very similar way as previously observed for their interaction with anionic phospholipid surfaces.
我们最近描述了抗磷脂综合征患者中抗心磷脂（aCL）和狼疮抗凝物（LA）抗体的体外作用机制。LA抗体抑制血浆中的凝血反应，因为它们似乎识别脂质结合的（人）凝血酶原复合物，而aCL抗体需要β2-糖蛋白I（β2-GPI）才能与阴离子磷脂结合。根据aCL抗体在脂质依赖性凝血反应中的行为，可将其分为两个亚组：A型aCL增强β2-GPI的抗凝作用，而B型aCL则不然。在本研究中，我们使用含有高度纯化的人源和牛源凝血因子Xa、Va和凝血酶原的检测系统，研究了纯化的A型和B型aCL以及LA抗体对钙离子载体激活的血小板和血小板衍生微泡的促凝活性的影响。在没有β2-GPI的情况下，两种类型的aCL均无法抑制血小板或微泡的凝血酶原酶活性。然而，当A型aCL抗体与β2-GPI联合添加时，在几分钟内观察到血小板和血小板衍生微泡的凝血酶原酶活性受到强烈且剂量依赖性的抑制。这种抑制作用也取决于β2-GPI的浓度。相反，在存在β2-GPI的情况下，未观察到B型aCL抗体对血小板（或微泡）凝血酶原酶活性有抑制作用。LA抗体能够以剂量依赖性方式抑制激活的血小板和血小板衍生微泡的促凝活性。对于两种LA制剂，只有在使用人凝血酶原作为底物时，这种抑制作用才明显，而第三种制剂在存在人凝血酶原和牛凝血酶原时均表现出抑制作用。数据表明，在各自的辅因子β2-GPI和凝血酶原存在的情况下，aCL和LA抗体与激活的血小板和血小板衍生微泡的膜相互作用的方式，与先前观察到的它们与阴离子磷脂表面的相互作用非常相似。
