Detection of immune complexes by monoclonal anti-C1q and anti-C3d ELISA systems

Abstract

By means of monoclonal anti-C1q and anti-C3d ELISA systems, circulating immune complexes (CIC) of patients with various collagen diseases were measured.
The positive frequencies and mean values of CIC detected by anti-C1q were 94% and 145.8μg/ml in active SLE, 50% and 52.5μg/ml in inactive SLE and 56.8% and 58.5μg/ml in RA.
On the other hand, CIC detected by anti-C3d were 67% and 20.0μg/ml in active SLE, 14% and 2.7μg/ml in inactive SLE and 21.6% and 6.1μg/ml in RA.
Levels of CIC detected by the both systems correlated positively with titers of anti-DNA antibodies and negatively with titers of serum CH50 in SLE.
In RA, levels of CIC detected by anti-C3d correlated positively with ESR and CRP, whereas those by anti-C1q did not. No correlations between levels of CIC detected by the both systems and titers of RF were observed.