Kallikrein inhibition and C₁-esterase inhibitor levels in patiens with the lupus inhibitor

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 lupus inhibitor. They found that kallikrein inhibition was greater than 100% of that of a normal plasma pool in all patients with greater than 125% in 11 of 19. Kallikrein inhibition was significantly correlated with C₁-esterase inhibitor (C₁-s-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.