Immunochemical determination of DNA in immune complexes present in the circulation of patients with systemic lupus erythematosus.

The presence of DNA antigen in circulating immune complexes formed with anti-DNA antibodies of IgG class was determined in sera of 138 SLE patients and 23 healthy donors, employing monoclonal anti-dsDNA antibodies in a quantitative dot blot assay. About half of the SLE patients had elevated amounts of DNA antigen in the immune complexes (presumably as nucleosomes). The number of patients with the SLE manifestations was not higher in the group with the high amount of DNA in immune complexes. Elevated levels of DNA in immune complexes was found only in sera of SLE patients with the active, as well as quiescent form, of the disease and not in sera of healthy donors. The presence of increased amounts of DNA antigen in circulating immune complexes could indicate the presence of SLE pathology even if no manifestations of SLE are found. The level of the circulating anti-DNA antibodies was not correlated with the amount of DNA in immune complexes.