Three Assays for the Characterization and Quantitation of Human Serum Amyloid A

Abstract

Two different radioimmunoassays (RIA) and an enzyme-linked immunosorbent assay (ELISA) were developed for the quantitation and antigenic characterization of [human] amyloid A (AA) and serum amyloid A (SAA) proteins, and the 3 assays were evaluated and compared with each other. Sensitivity, reproducibility, effect of denaturation and storage of serum and range of determination were considered. All 3 assays were useful, but for different purposes. The most suitable method for the determination of SAA in whole serum was a 2nd antibody precipitation RIA with purified SAA as labeled tracer and standard, and polyclonal rabbit anti-SAA as 1st antibody. This assay provided SAA concentrations in absolute amounts (mg/l) and acceptable reproducibility without need for prior denaturation of serum. Both advantages and disadvantages of ELISA using monoclonal antibodies to SAA and a solid-phase RIA using AA, SAA, anti-AA and anti-SAA were observed. The 3 assays were suitable for antigenic studies of AA and SAA.