title: A sensitive method to assay blood complement C1- inhibitor activity.
abstract: Hereditary angioneurotic edema results from deficiency of complement protein C1- inhibitor. Using a new spectrophotometric assay for C1-s esterase activity on the N-alpha-benzoyl-L-arginine ethyl ester, we describe a routinely available method for quantifying low C1- Inhibitor functional activities in EDTA-treated plasma of hereditary angioneurotic edema patients. C1- Inhibitor activity is deduced from the residual esterase activity of C1-s incubated with 20-80 microliters plasma samples. Arbitrary units (volume of sample inhibiting 50% of C1-s activity) were used to express C1- Inhibitor normal activity which was estimated as 22,500 +/- 5,000 (SD) U/l in 45 healthy individuals. The correlation with C1- Inhibitor antigen in these healthy individuals and 89 patients with varying concentrations of C1 Inhibitor ranging from 0.05-1.05 g/l was r = 0.91. Levels down to 2,000 U/l could be estimated. Specific inhibitory activity is an absolute requirement to distinguish between type I and type II hereditary angioneurotic edema.
authors.affiliation: Laboratoire d'Immunologie, Hôpital Sud, CHU Grenoble, Echirolles, France.
authors.forename: C
authors.initials: C
authors.lastname: Drouet
authors.forename: C
authors.initials: C
authors.lastname: Alibeu
authors.forename: D
authors.initials: D
authors.lastname: Ponard
authors.forename: G J
authors.initials: GJ
authors.lastname: Arlaud
authors.forename: M G
authors.initials: MG
authors.lastname: Colomb
mesh_terms: D003174:Complement C1 Inactivator Proteins / Q000097:blood*; D003173:Complement C1s / Q000032:analysis; D006801:Humans; D013056:Spectrophotometry, Ultraviolet / Q000379:methods
chemical_list: D003174:Complement C1 Inactivator Proteins; D003173:Complement C1s