Changes in the glycosylation of IgG in the collagen-induced model of arthritis

It is now well established that rheumatoid arthritis patients have reduced levels of galactose on their immunoglobulin G (IgG) molecules compared with normal individuals. We have investigated whether, in an experimentally induced model of arthritis, similar glycosylation changes on IgG are to be found. Serum IgG was isolated from collagen-induced arthritic DBA/1 mice and a control group, and the glycosylation of the IgG in these preparations was compared using lectin blotting. The glycosylation of IgG in immune complexes was also analysed. Arthritic mice exhibited similar glycosylation changes on their IgG as observed for rheumatoid arthritis patients. On average, there was less galactose on the IgG from arthritic mice than from the control group, but this difference was of borderline significance. However, theN-acetylglucosamine content of IgG was significatly elevated in arthritic mice. There was no difference in the sialic acid content of IgG in the two groups. The results for immune complexes were similar to those obtained for serum IgG, but the data were limited by insufficient numbers. The similarity in glycosylation changes in collagen-induced arthritis and in patients with rheumatoid arthritis suggests that common pathogenic mechanisms may be involved.