Binding of human monoclonal IgG rheumatoid factors to Fc is influenced by carbohydrate.
OBJECTIVE
The precise nature of the epitope on the Fc portion of the IgG molecule to which IgG rheumatoid factors (RF) bind has not been identified. As patients with rheumatoid arthritis (RA) have abnormal glycosylation of the Fc portion of IgG, we investigated the impact of the sugar present in the Fc on the binding of IgG RF.


METHODS
Binding of monoclonal IgG RF to Fc fragments with varying oligosaccharide chains was detected using an immunoblot assay.


RESULTS
We demonstrated that the binding of human hybridoma derived monoclonal IgG RF was strongly influenced by the presence of carbohydrate and was maximal when the carbohydrate molecule was intact. The RF did not bind directly to the carbohydrate moiety itself.


CONCLUSIONS
This suggests that conformational changes in the polypeptide chain induced by the carbohydrate are responsible for the observed binding patterns.
Newkirk
M M
MM
Department of Medicine, McGill University, Montreal General Hospital Research Institute, PQ, Canada.
Rauch
J
J
D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000276:immunology*; D002241:Carbohydrates / Q000032:analysis*; D005260:Female; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology*; D012217:Rheumatoid Factor / Q000737:chemistry* / Q000276:immunology*
D000911:Antibodies, Monoclonal; D002241:Carbohydrates; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D012217:Rheumatoid Factor