Correlation between IgG class of rheumatoid factors, immune complexes and C-reactive protein in human sera containing RF

We measured the concentration of three immunoglobulin classes of rheumatoid factors (Ig-RFs), C3d binding IgG immune complex (C3d-IC), Clq binding IgG immune complex (Clq-IC) and C-reactive protein (CRP) in 74 samples of human sera with high levels of RF (24.0-2350.0 IU/mI). In sera with high levels of C3d-IC (> 15.0,ug/ml), there was a positive correlation between the levels of CRP and the IgG-RF, but there was no correlation between the levels of CRP and the immune complexes (C3d-IC and Clq-Ie). And then, there was a positive correlation between the levels of CRP and IgG-RF or C3d-IC and IgG-RF when the levels of Clq-IC in patients sera were higher than 80.0 ,ug/ml. However, there was no correlation between the levels of CRP and Clq-IC in these patients sera containing high levels of both C3d-IC and Clq-Ie. These results indicated that the determination of C3d-IC, Clq-IC, IgG-RF and CRP in human sera containing RF denote different implications as inflammatory indexes on progression of rheumatoid arthritis and other autoimmune diseases.