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: C Drouet, C Alibeu, D Ponard, G J Arlaud, M G Colomb
• Journal: Clinica chimica acta; international journal of clinical chemistry (Clin Chim Acta) Vol. 174 Issue 2 Pg. 121-30 (May 31 1988) ISSN: 0009-8981 [Print] Netherlands
• PMID: 3260154 (Publication Type: Journal Article)

Chemical References

• Complement C1 Inactivator Proteins
• Complement C1s

Topics

• Complement C1 Inactivator Proteins (blood)
• Complement C1s (analysis)
• Humans
• Spectrophotometry, Ultraviolet (methods)