Complement and Contact System Parameters in Healthy Subjects and HANE Patients in Basal Condition Healthy subjects Type - I HANE

Ci inhibitor (Ci-Inh) catabolism in plasma of patients with hereditary angioneurotic edema (HANE) was assessed by measuring the complexes formed by Cl-Inh with its target proteases (Cis, Factor XIIa, and kallikrein) and a modified (cleaved) inactive form of Ci-Inh (iCI-Inh). This study was performed in plasma from 18 healthy subjects and 30 patients with HANE in remission: 20 with low antigen concentration (type I) and 10 (from 5 different kindreds) with dysfunctional protein (type II). Both type-I and type-II patients had increased Ci-Ci-Inh complexes (P < 0.0001), which in type I inversely correlated with the levels of Cl-Inh (P < 0.001). iCI-Inh was normal in all type-I patients and in type-I1 patients from three families with increased Ci-Inh antigen, whereas iCi-Inh was higher than 20 times the normal values in patients from the remaining two families with Ci-Inh antigen in the normal range. None of the subjects had an increase of either Factor XIIa-Ci-Inh or kallikrein-Ci-Inh complexes. This study shows that the hypercatabolism of Ci-Inh in HANE patients at least in part occurs via the formation of complexes with Ci and that genetically determined differences in catabolism of dysfunctional Ci-Inh proteins are present in type-II patients. (J. Clin. Invest. 1990. 85:1215-1220.) complement* contact system * Ci inhibitor catabolism * Ci inhibitor deficiency * dysfunctional Ci inhibitor