DNA levels in circulating immune complexes decrease at severe SLE flares -Correlation with complement component C1q

The objective of this study was to investigate the relationship of DNA cont ent in circulating immune complexes with disease course and activity in SLE . The DNA content in circulating immune complexes containing anti-DNA antib odies of IgG class was determined in serial samples from 28 patients with S LE by a quantitative immunochemical assay. The patients presented various a ctive disease manifestations over 5-55 months. Disease activity (SLEDAI-sco re), drug treatment and ACR-criteria were recorded. Levels of anti-dsDNA, C RP, leukocytes, complement components C3, C4 and C1q were measured. Patient s with severe flares and high SLEDAI scores had low C1q levels at onset of active disease manifestations. The patients with low C1q serum levels durin g flare (n = 13) had significantly lower amounts of DNA in immune complexes than patients with normal C1q (P = 0.001). Levels of DNA in immune complex es correlated with C1q at flares (r = 0.62, P < 0.0001) and correlated inve rsely with SLEDAI scores (r = -0.47, P = 0.012). in conclusion, the low lev els of DNA in circulating immune complexes found in severely ill SLE patien ts with concomitantly low serum concentrations of C1q prior to flares might be related to tissue deposition of immune complexes. (C) 1999 Academic Pre ss.