37] Detection and quantitation of immune complexes with a rapid polyethylene glycol precipitation complement consumption method (PEG-CC)

Abstract

Publisher Summary This chapter discusses the detection and quantitation of immune complexes (IC) with a rapid polyethylene glycol precipitation complement consumption method (PEG-CC). Some assays make use of the isolation of IC through a polyethylene glycol precipitation step. This approach for physicochemical isolation of IC is combined with a simple one-tube, two-step complement consumption procedure for the quantitation of the precipitated and redissolved IC. The precipitable IC activity amounted to 90%-95% after 60 min and 95%-100% after 90 min, as compared to the values obtained after incubation at 4° for 18 hr. For practical reasons, 90 min was chosen for the standardized assay. There were no convincing differences in the reactivity of normal and patient sera or in the precision, when the precipitate was washed with 1ml of 3.0–5.0% PEG and redissolved for 30 min at 22°. The PEG-CC assay has been used to monitor a variety of patient categories and high concentrations of IC have been found in acute SLE, primary biliary cirrhosis, mixed cryoglobulinemia, and in more than 90% of the patients with active classical sero-positive rheumatoid arthritis.