Detection of IgG rheumatoid factor by concanavalin A treatment and complement fixation with IgG rheumatoid factor.
Concanavalin A (Con A) froms precipitates with carbohydrate-rich protein such as IgM, IgD, IgE, and IgA. Since IgG contains little carbohydrate and does not react with Con A, the activity of IgG-rheumatoid factor (RF) can be measured in the supernate of the Con A-treated serum. When the latex fixation test (LFT) and the sensitized sheep cell agglutination test (SSCA) were perfromed in the supernate for the detection of IgG-RF, LFT was positive in 32-1% of sera, out of 137 sera originally positive for LFT, and SSCA was positive in 18-5% of sera, out of 119 sera originally positive for SSCA. IgG-RF exhibited lower complement fixing ability than IgM-RF and correlated with agglutination titres of IgG-RF, while the CH50 of the original serum did not correlate with haemolytic activities of either IgM-RF or IgG-RF.
D001172:Arthritis, Rheumatoid / Q000276:immunology*; D003168:Complement Fixation Tests; D003208:Concanavalin A; D006801:Humans; D007070:Immunoglobulin A / Q000032:analysis; D007074:Immunoglobulin G / Q000032:analysis*; D007075:Immunoglobulin M / Q000032:analysis; D008757:Methylglucosides; D012217:Rheumatoid Factor / Q000032:analysis*
D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D008757:Methylglucosides; D003208:Concanavalin A; D012217:Rheumatoid Factor