To determine the normal range of antiagalactosyl IgG antibodies in healthy children, and to investigate the utility of determination of antiagalactosyl IgG antibodies in patients with juvenile idiopathic arthritis (JIA) and juvenile onset Sjögren's syndrome (SS).
Serum concentrations of antiagalactosyl IgG antibodies were measured in 225 healthy children, 68 patients with JIA (systemic arthritis in 21, polyarthritis in 29, oligoarthritis in 18), and 15 patients with juvenile onset SS, using a lectin-enzyme immunoassay employing prepared human agalactosyl IgG as antigen. A comparison was made between the prevalence and utility of antiagalactosyl IgG antibodies in patients and those of conventional rheumatoid factors (RF) determined by laser nephelometry.
The average serum concentration of antiagalactosyl IgG antibodies for healthy controls was 2.41 +/- 0.93 arbitrary units (AU)/ml, and the cutoff value of the normal range was set at 4.3 AU/ml (mean + 2 SD). As a result, antiagalactosyl IgG antibodies were positive in 25 (37%) of 68 patients with JIA, and 14 (93%) of 15 patients with juvenile onset SS, in whom values were much higher than the frequencies of RF positivity. The serum concentrations of antiagalactosyl IgG antibodies in patients were closely correlated with those of RF. Thirteen patients with JIA and 6 patients with juvenile onset SS were positive for antiagalactosyl IgG antibodies despite being negative for RF. With regard to prognosis during followup periods of at least 5 years, JIA patients positive for antiagalactosyl IgG antibodies, even if negative for RF, were resistant to treatment. However, positivity for antiagalactosyl IgG antibodies had no relation to joint destruction.
Our data suggest that antiagalactosyl IgG antibodies, compared with RF, show higher sensitivity to detect immunological disorders in JIA and juvenile onset SS.