Detection of circulating immune complexes with a Raji cell enzyme immunoassay

The Raji cell assay for circulating immune complexes (CIC) is frequently the method of choice when the detection of large, complement fixing complexes is desired. We have developed an enzyme-linked immunosorbent assay modification (Raji-ELISA) of the Raji cell technique which is easy to perform, uses commercially available reagents and is more convenient than the conventional Raji cell radioimmune assay (Raji-RIA). Fourteen samples were tested by both assays and a good correlation was observed (P = 0.05). Sera from patients with suspected immune complex associated diseases were tested in the Raji-ELISA. Unsensitized Raji cells gave a value of 1.25 micrograms of immune complex associated IgG/ml. Using 2 standard deviations as a cutoff to determine positivity, 2 of 32 healthy controls (6.2%) had elevated levels of circulating immune complexes. In our study population, 9 of 23 cancer patients (39.1%), 10 of 13 patients with autoimmune diseases (76.9%), 3 of 17 patients with positive rheumatoid factor titers (17.6%), 1 of 23 pregnant patients (4.3%), 1 of 5 preeclamptic patients (20%) and 9 of 30 other patients with suspected immune complex associated diseases (30%) had elevated levels of CIC.