Anticardiolipin Antibodies in Patients With Pregnancy Loss Induce Factor Xa Production in the Presence of (β2‐Glycoprotein I

PROBLEM: Anticardiolipin antibodies (aCL) are commonly associated with recurrent pregnancy loss, though the mechanism is uncertain. Some investigators have indicated that aCL may be directed at a complex made up of cardiolipin and a blood anticoagulant, β2‐glycoprotein I (β2GPI). We therefore investigated the effects of β2GPI‐dependent aCL IgG enriched fractions, isolated from sera of patients with pregnancy losses, on blood coagulation. METHOD: β2GPI‐dependent aCL were prepared from sera of three women with second trimester pregnancy losses, by cardiolipin affinity column chromography, following by anti‐β2GPI affinity column chromatography. The effects of β2GPI and β2GPI‐dependent aCL on the activation of factor X in vitro were examined. RESULTS: β2GPI inhibited the activation of factor X and β2GPI‐dependent aCL blocked this inhibitory effect in a dose dependent manner. CONCLUSION: These results imply the possibility of β2GPI‐dependent aCL induce hypercoagulation or thrombus by blocking the inhibitory effect of β2GPI on activation of factor X, which may result in pregnancy loss. 1995 Munksgaard