PMID: 2508795Nov 15, 1989Paper

Impaired catalytic function of activated protein C: a new in vitro manifestation of lupus anticoagulant.

Blood
E Marciniak, E H Romond

Abstract

Lupus anticoagulant (LA), an antibody against anionic phospholipid with anticoagulant laboratory manifestations, is paradoxically associated with a high incidence of thrombosis. In the present study we analyzed the phospholipid- and platelet-dependent degradation of factor Va following clotting in plasma from 15 consecutive patients with LA to provide evidence for a distinct procoagulant effect of the antibody. After clotting with 25 micrograms phospholipid/mL, all samples containing LA showed markedly decreased rates of factor Va degradation (k = 0.01 to 0.14 min-1 v 0.27 to 0.35 min-1 in controls). Also with higher phospholipid concentrations (up to 100 micrograms/mL), as well as in the presence of platelets (5 to 33 x 10(7)/mL), significantly less of the procoagulant activity disappeared per unit of time in samples with LA than in controls. Plasma with LA was to a variable extent capable of decreasing or abolishing factor Va inhibition in normal plasma. Most importantly, exogenous activated protein C failed to correct the ineffective factor Va destruction despite adequate protein S levels. These data suggest that LA prevents the formation of the complex essential for rapid proteolysis of factor Va both on phospholipid and on...Continue Reading

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