Studies on circulating immune complexes. I: Circulating immune complexes in various types of glomerulonephritis and collagen disease: a comparative study employing conglutinin solid phase radioimmunoassay and raji cell radioimmunoassay.

Abstract

A study was undertaken to examine the differences in serum levels of circulating immune complexes (CIC) detected by different methods in various types of collagen disease and primary glomerulonephritis. The subjects used were 16 patients with SLE, 22 with IgA nephropathy, 8 with membranoproliferative glomerulonephritis, 8 with membranous nephropathy, 6 with minimal change nephrotic syndrome, and 2 each with RA, PSS, DM, Sjögren syndrome, PN, MCTD and overlap syndrome, respectively. CIC were measured by two assays, namely, bovine conglutinin solid phase radioimmunoassay (C-assay) and Raji cell radioimmunoassay (R-assay). In SLE, the incidence and amounts of CIC detected were higher in R-assay than in C-assay. Similar results were obtained for the other types of collagen diseases. Furthermore, a discrepancy in the incidence of CIC detected by the two assays was found in 30% of patients with collagen diseases. Concerning the detection of CIC in primary glomerulonephritis, the sensitivity of C-assay was higher than that of R-assay. This discrepancy appears to reflect the different sensitivities of the two assays. No significant correlation was found between the CIC level and the intensity of IgG deposits in various types of glomerulonephritis. These results suggest that the R-assay was better for the detection of CIC in collagen diseases, and that the C-assay was suitable for that in primary glomerulonephritis.