An anticoagulant activity was isolated from the plasma of a patient with a strong
lupus-like anticoagulant using gel filtration by high performance liquid chromatography.
IgM were detected in this anticoagulant fraction which exhibited specificity towards
50% phosphatidylcholine - 50% phosphatidylserine vesicles and cardiolipin. These phospholipids
were able to produce an apparent 3-fold enhancement of purified human protein C activation
by human a-thrombin in the presence of purified human placenta thrombomodulin. In
the absence of phospholipid, the anticoagulant fraction had no effect on thrombomodulin
activity. The anticoagulant fraction could neutralize the enhancement of thrombomodulin
activity by phospholipid in a dose-dependent manner. This study suggests that the
neutralization of phospholipid might result in a reduced activation of protein C which
could be responsible for the occurrence of thrombotic complications in a proportion
of patients with lupus anticoagulants.
Keywords
Lupus anticoagulant - Thrombosis - Phospholipid - Thrombomodulin - Protein C