Role of IgM & IgA rheumatoid factors in complement activation in patients with juvenile rheumatoid arthritis

We studied the relationship between the degree of complement activation in juvenile rheumatoid arthritis (JRA) with the levels of circulating IgM and IgA rheumatoid factors (RF). Forty children with JRA and 25 matched control s were included in the study. Levels of C3d (a degradation product of compl ement component C3), circulating immune complexes (CICs), IgM RF and IgA RF were measured by ELISA. Levels of C3d, CICs, IgM RF and IgA RF were elevat ed in patients with JRA as compared to controls. Levels of C3d had a linear relationship with levels of CICs (P<0.05) but not with levels of circulati ng IgM RF and IgA RF. Thus, complement activation occurs in children with J RA and is associated with raised levels of CICs but not with levels of circ ulating IgM and IgA RF. Circulating IgM and IgA RF have little, if any, rol e in complement activation observed in patients with JRA.