title: Specific, sensitive, precise, and rapid functional chromogenic assay of activated first complement component (C1) in plasma.
abstract: We present a new functional assay for the first complement component (C1) in plasma, based on its activation by inhibition of the C1-esterase inhibitor (C1-inh) when monospecific antiserum to C1-inh is added to the plasma. After maximal activation, we can determine the concentration of activated C1 by using an amidolytic rate assay with a chromogenic substrate. We have optimized the assay conditions with respect to incubation time, concentration of antiserum to C1-inh, ionic strength, and pH. Our method determines specifically the concentration in plasma of free activated C1, not complexes of activated C1 with C1-inh, and is not influenced by the concentration of C1-inh in the test sample. Concentrations of C1 correlated significantly with activities determined by a hemolytic assay (r = 0.55, t = 4.09, P less than 0.001). The estimated interassay CV was 5% and the intra-assay CV was 1%. The sensitivity, imprecision, and practical test performance of our assay are superior to those of conventionally used hemolytic assays.
authors.affiliation: Department of Clinical Chemistry, Ribe County Hospital, Esbjerg, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Munkvad
authors.forename: J
authors.initials: J
authors.lastname: Jespersen
authors.forename: J
authors.initials: J
authors.lastname: Sidelmann
authors.forename: J
authors.initials: J
authors.lastname: Gram
mesh_terms: D000328:Adult; D000906:Antibodies / Q000494:pharmacology; D002863:Chromogenic Compounds; D003167:Complement Activation / Q000187:drug effects; D003172:Complement C1 / Q000032:analysis* / Q000592:standards; D003174:Complement C1 Inactivator Proteins / Q000276:immunology; D015941:Complement Hemolytic Activity Assay; D003240:Connective Tissue Diseases / Q000276:immunology; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007106:Immune Sera / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D018805:Sepsis / Q000276:immunology
chemical_list: D000906:Antibodies; D002863:Chromogenic Compounds; D003172:Complement C1; D003174:Complement C1 Inactivator Proteins; D007106:Immune Sera