Measurement of circulating immune complexes using Fc receptors on guinea pig peritoneal exudate cells. Part 2. Measurement of circulating immune complexes in patients with systemic lupus erythematosus, rheumatoid arthritis and thyroid diseases.

Circulating immune complexes have been detected in patients with systemic lupus erythematosus(SLE), rheumatoid arthritis(RA), Graves' disease and Hashimoto's disease by a newly established method using guinea pig peritoneal exudate cells. This method discriminated 75.0% of the SLE, 72.4% of the RA, 50.0% of the Graves' disease and 40.0% of the Hashimoto's disease patients from normal controls. IC levels correlated significantly with CH50, slightly with anti DNA antibody, but with neither the ANF staining pattern nor the degree of renal damage assessed by FAT findings in SLE patients. No correlation was observed between disease activity and IC levels in patients with RA. Elevated levels of IC were detected in some patients with thyroid disease by this method, but not by the Clq solid phase enzyme immunoassay. Serum fractionation with a Sepharose 6B column revealed that the molecular weight of the substance which this method can detect is larger than 19S. This method is not interfered with by γ-globulin nor the rheumatoid factor in serum. This is a simple, sensitive and the only practical method among the methods using Fc receptors