Inhibition of Protein C Activation by Endothelial Cells in the Presence of Lupus Anticoagulant

Abstract

To the Editor: The lupus anticoagulant is frequently associated with thrombosis. This is unexplained, except that it may result from the hypothetical effect of IgG fractions from patients with the anticoagulant on prostacyclin production by endothelial cells.¹ We investigated the effect of IgG fractions from three patients with the lupus anticoagulant on the rate of protein C activation in cultured human endothelial cells from veins in the umbilical cord. All patients with the lupus anticoagulant had recurrent thrombotic episodes, as has frequently been reported in such cases.² Confluent endothelial cells were incubated for one hour at 37°C, with buffer (medium . . .