Kallikrein Inhibition and C1-Esterase Inhibitor Levels in Patients with the Lupus Inhibitor

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Abstract
It has been suggested that kallikrein inhibition may predispose patients with the lupus inhibitor to thrombosis by interfering with the Factor XII–mediated activation of plasminogen. To further investigate this suggestion, the authors measured kallikrein inhibition in 19 patients with the lupus inhibitor. They found that kallikrein inhibition was greater than 100% of that of a normal plasma pool in all patients and greater than 125% in 11 of 19. Kallikrein inhibition was significantly correlated with C1-esterase inhibitor (C1s-INH) concentration, which they measured by rocket immunoelectrophoresis (r = +0.55, P < 0.05). In three patients the C1s-INH was more than 30% greater than the kallikrein inhibition. Crossed immunoelectrophoresis for C1s-INH in these patients’ plasma revealed an electrophoretic mobility identical with that of the normal plasma pool. The authors suggest that C1s-INH-mediated kallikrein inhibition, in conjunction with other coagulation abnormalities, predisposes patients with the lupus inhibitor to thrombosis.