C1 inhibitor infusion modifies platelet activity in hereditary angioedema patients.

Abstract Context.—C1 inhibitor (C1-INH) is an α2-globulin that blocks esterolytic activity of the first component of the classic complement cascade. The α-granules of normal human platelets also contain C1-INH, which is expressed on the platelet surface during platelet secretion in healthy patients, but it is clearly reduced in patients with hereditary angioedema (HAE). Objective.—To evaluate the effects of in vivo C1-INH concentrate infusion on platelet responsiveness and coagulation system activity in patients with HAE. Design.—Assessment of the platelet activity and plasma levels of C1-INH, activated factor XII (XIIa), and prothrombin fragment F1.2 (F1.2) before and after infusion of 15 U/kg of C1-INH concentrate. Patients.—In 6 patients (4 men and 2 women), HAE was diagnosed according to the accepted clinical and laboratory criteria. Measurements.—Platelet aggregation (final concentrations: adenosine diphosphate, 0.5, 1.25, and 2.5μM; collagen, 5 μg/mL), C1-INH antigen (radial immunodiffusion), C1-INH...