Detection of disease-specific augmentation of abnormal immunoglobulin G insera of patients with rheumatoid arthritis

Galactose-free immunoglobulin G (IgG), which is known to be higher in the s era of patients with rheumatoid arthritis, was prepared from IgG of healthy Volunteers using enzymes. Its reactivity to lectins was analyzed. The gala ctose-free IgG showed no reactivity to Ricinus communis agglutinin 120 but displayed greater reactivity to concanavalin A and Lens culinaris lectin th an did intact human IgG. Then, IgG in serum samples was bound to protein A immobilized on a nitrocellulose membrane, and its reactivity to biotinylate d concanavalin A was measured with streptavidin-conjugated horseradish pero xidase. When the reactivity to concanavalin A of IgG in sera from healthy i ndividuals and patients with rheumatoid arthritis (RA), osteoarthritis, sys temic lupus erythematosus, or hepatic disease was compared, higher levels w ere shown in patients with RA, notably in 60% of the seronegative patients and 80% of the early phase patients. Therefore, it was suggested that augme ntation of the abnormal IgG in sera was highly specific to patients with RA and that this novel serum test could be very useful for an accurate diagno sis of this disease.