Specific detection of circulating DNA:anti-DNA immune complexes in human systemic lupus erythematosus sera using murine monoclonal anti-DNA antibody.

The presence of DNA-anti-DNA immune complexes in sera from patients with systemic lupus erythematosus (SLE) was investigated by a new solid phase radioimmunoassay (RIA). This assay used murine monoclonal anti-double stranded DNA (dsDNA) antibody to recognize DNA present in the complexes and 125I-rabbit anti-human gamma globulin as a tracer. DNA-anti-DNA immune complexes were found in certain SLE sera but not in sera from patients with other immune complex diseases and from healthy blood donors. The presence of circulating DNA-anti-DNA complexes was associated with low C4 levels. It was not related to the presence of immune complexes detected by the polyethylene glycol assay suggesting either that the assay did not detect all DNA-anti-DNA complexes or that other antigen-antibody systems constitute the major immune complex components in SLE sera. The clinical significance of circulating DNA-anti-DNA complexes in SLE sera as well as the potential use of this solid phase RIA using various monoclonal antibodies to detect specific antigen-antibody systems is discussed.