Anomalous Raji cell activity related to DNA binding in some patients with autoimmune disease

We examined sera from patients with autoimmune disease that showed a discrepancy between the Raji cell assay and other tests for circulating immune complexes where the Raji cell activity was highly elevated. Using gel filtration chromatography, we found that the Raji cell activity was associated with monomeric IgG and little evidence of aggregates in the samples. Samples elevated for circulating immune complexes by all tests showed aggregates with associated Raji cell activity. The activity in discrepant samples was decreased by up to 40% by absorption of the IgG fraction with DNA-cellulose prior to the Raji cell assay. It is suggested that binding by autoantibodies to the Raji cell membrane is due to a variety of mechanisms.