A monoclonal antibody raised by immunising mice with group A streptococci binds to agalactosyl IgG from rheumatoid arthritis.

It was shown recently that the IgG of patients with rheumatoid arthritis tends to lack the terminal galactose normally present on the conserved N-linked oligosaccharide situated on the CH2 domain. This results in the exposure of a terminal N-acetylglucosamine linked beta 1-2 to mannose. It is reported here that mice immunised with the peptidoglycan/polysaccharide complex of group A streptococci can be used as a source of monoclonal antibodies binding to this epitope. It may be significant that the organism responsible for rheumatic fever evokes antibodies binding to an abnormality of IgG found in rheumatoid arthritis.