CIRCULATING IMMUNE-COMPLEX ASSAYS IN PATIENTS WITH LUPUS AND MEMBRANOUS GLOMERULONEPHRITIS

We have studied patients with both lupus and membranous glomerulonephritis for the presence of circulating immune complexes using Raji cell radioimmunoassay, solid phase Clq binding radioimmunoassay, and the serum cryoglobulins. Our results show proliferative lupus glomerulonephritis to be associated with greater levels of circulating immune complexes than either lupus or nonlupus membranous glomerulonephritis. The serum cryoglobulins were the most frequently positive assays followed by the Clq binding assay and Raji cell assay. The different immune complex assays appeared to measure overlapping, but not identical, material. Cryoprecipitable immune complexes are more reactive in the Raji cell assay than the Clq binding assay. In both assays however, removal of cryoprecipitable material from serum caused a significant decrease in reactivity. Sucrose density gradient ultracentrifugation analysis of serum further indicated that most of the immune complex activity was of low molecular weight. Our results also suggest that a single immune complex assay may not be adequate for complete characterization of circulating immune complexes in a given disease. © 1979.