RAT SPLEEN LEUKOCYTE (RSL) RADIOIMMUNOASSAY FOR THE DETECTION AND QUANTIFICATION OF SOLUBLE IMMUNE-COMPLEXES

Abstract

A simple and sensitive method for the detection and quantification of soluble immune complexes in sera was developed by utilizing Fc receptors on rat spleen leukocyte (RSL). Aggregated human Ig[immunoglobulin]G (AHG) was used as an in vitro model of immune complexes and its uptake by RSL was quantified using 125I-anti-human IgG. RSL bound AHG in medium and in EDTA inactivated and absorbed serum. The limit of detection of this method was 2 .mu.g AHG/ml in medium and 4 .mu.g AHG/ml in serum. Sera samples from patients with thyroid disorders and from diabetics were incubated with RSL and the cells incubated with 125I-anti-human IgG. The amount of label bound to the cells was determined and referred to a standard curve of radiolabeled antibody [Ab] uptake by cells previously incubated with varying amounts of AHG in serum. The results obtained were compared with those obtained using the Raji[human Burkitt''s lymphoma]-cell radioimmunoassay. Human anti-rat erythrocyte Ab was detected in normal human serum. The amount of complexes formed in serum by heat treatment was quantified by this method.