title: Quantitation of the anaphylatoxin C3a in the presence of C3 by a novel sandwich ELISA using monoclonal antibody to a C3a neoepitope.
abstract: C3a levels in plasma are usually measured by a competitive inhibition radioimmunoassay (RIA) using 125I-labelled C3a-desArg and antibodies to C3a capable of detecting C3a determinants which are also present on the native C3. Therefore, prior to the assay native, non-cleaved C3 has to be removed completely from the C3a-containing sample by precipitation. We developed a new rapid two-site sandwich ELISA system for the quantitation of C3a-desArg in plasma. This immunoassay uses a monoclonal antibody (mAb H466) reacting with C3a-desArg but not with C3. The reactivity of mAb H466 with a neoantigenic determinant of C3a-desArg permitted the direct quantitation of C3a-desArg without removal of C3 from the sample. The mAb H466 was used as a capture antibody and bound C3a-desArg was detected with a second peroxidase-labelled anti-C3a mAb. The lower limit of detection of C3a-desArg in this ELISA was 1 ng/ml. The C3a-desArg levels measured in the plasma samples of various patients were found to differ over a wide range. A good correlation was observed between the results obtained in the RIA and those obtained in the ELISA (r = 0.95). High levels of C3a-desArg were detected in plasma from patients with multiple trauma and patients undergoing haemodialysis. The C3a-desArg assay described should facilitate the routine quantitation of C3a in samples of plasma.
authors.affiliation: Institute for Immunology, University of Heidelberg, F.R.G.
authors.forename: G
authors.initials: G
authors.lastname: Zilow
authors.forename: W
authors.initials: W
authors.lastname: Naser
authors.forename: R
authors.initials: R
authors.lastname: Rutz
authors.forename: R
authors.initials: R
authors.lastname: Burger
mesh_terms: D000911:Antibodies, Monoclonal; D003176:Complement C3 / Q000031:analogs & derivatives* / Q000032:analysis* / Q000276:immunology; D015926:Complement C3a; D004492:Edetic Acid / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D011863:Radioimmunoassay
chemical_list: D000911:Antibodies, Monoclonal; D003176:Complement C3; C044541:complement C3a, des-Arg-(77)-; D015926:Complement C3a; D004492:Edetic Acid