RESUMO
Serum IgG from rheumatoid arthritis patients contains a decreased number of oligosaccharide structures ending in galactose and thus there is an increase in N-acetylglucosamine as the terminal sugar, compared with healthy individuals. The relationship between these two sugars varies depending on the disease examined: IgG from patients with rheumatoid arthritis, juvenile onset chronic arthritis and Crohn's disease are at one extreme, and exhibit a reciprocal galactose:N-acetylglucosamine relationship, while Sjögren's syndrome and osteoarthritis IgG are at the other extreme, exhibiting a parallel increase in the expression of both galactose and N-acetylglucosamine. These results may occur as a consequence of more than one glycosylation site which is differentially glycosylated, but more likely by changes in the level of bisecting N-acetylglucosamine.