title: Improved method for measuring C1-r-C1-s-(C1 inh)2 complexes by an enzyme-linked immunosorbent assay.
abstract: Measurement of C1-r-C1-s-(C1 inh)2 complexes in serum or plasma by enzyme-linked immunosorbent assay (ELISA) has been proposed as a relatively convenient and sensitive means for assessing C1 activation. However, interference by unactivated C1q (r-s)2 at low serum or plasma dilutions has resulted in estimates that vary widely with the degree of serum or plasma dilution. Precipitating the interfering C1q (r-s)2 with 6% polyethylene glycol has been proposed to resolve this problem, but here it is shown that this procedure also precipitates or coprecipitates some of the C1-r-C1-s-(C1 inh)2 complexes. Satisfactory results have been achieved without PEG precipitation by testing high plasma dilutions under conditions where there is a sufficient excess of anti-C1s coating the microtitration plate wells that removal of C1q (r-s)2 is not necessary. Optimizing conditions for quantitating these complexes at high dilution have been investigated. The mean normal EDTA plasma C1-r-C1-s-(C1 inh)2 complex measurement was 36.6 +/- 7.0 (S.D.) ELISA units with a 95% confidence interval of 19.5-47.6u. Besides providing a sensitive assay for C1 activation, measuring C1-r-C1-s-(C1 inh)2 complexes may help to clarify the pathophysiologic mechanisms resulting from C1 inh deficiency under various conditions.
authors.affiliation: Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: K P
authors.initials: KP
authors.lastname: Mathews
authors.forename: J H
authors.initials: JH
authors.lastname: Herschbach
authors.forename: S L
authors.initials: SL
authors.lastname: Chambers
authors.forename: B L
authors.initials: BL
authors.lastname: Zuraw
mesh_terms: D000328:Adult; D011232:Chemical Precipitation; D003167:Complement Activation; D003174:Complement C1 Inactivator Proteins / Q000032:analysis*; D015922:Complement C1q / Q000302:isolation & purification; D015923:Complement C1r / Q000032:analysis*; D003173:Complement C1s / Q000032:analysis*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006801:Humans; D007201:Indicator Dilution Techniques; D008297:Male; D008875:Middle Aged; D011092:Polyethylene Glycols
chemical_list: D003174:Complement C1 Inactivator Proteins; D011092:Polyethylene Glycols; D015922:Complement C1q; D015923:Complement C1r; D003173:Complement C1s