Analysis of agalacto-IgG in rheumatoid arthritis using surface plasmon resonance

It is well established that IgG from rheumatoid arthritis (RA) patients are less galactosylated than IgG from normal individuals. Determination of aga lacto-IgG may therefore aid in diagnosis and treatment of RA. The decrease in galactosylation of IgG leads to an increase in terminal N-acetylglucosam ine residues, which can be detected using a specific lectin from Psathyrell a velutina. In the present study IgG from RA and control serum was purified using affinity chromatography. The samples were then, after reduction, ana lyzed on a BIOCORE (R) 2000 system with immobilized Psathyrella velutina le ctin. Using this technique it was possible to discriminate between IgG from RA patients and IgG from control individuals with respect to its content o f IgG with terminal N-acetylglucosamine. The affinity biosensor technique m akes it possible to detect binding without labeling or using secondary anti bodies.