Effect of infliximab on the glycosylation of IgG of patients with rheumatoid arthritis

In patients with rheumatoid arthritis (RA) a decrease in the terminal galactose content of N-linked glycans of the Fc region of agalactosyl immunoglobulin G (IgG) (GO) occurs. The aim of this study was to evaluate, for the first time, the effect of infliximab, a new monoclonal antibody for the treatment of RA, on this phenomenon. A total of 19 patients with active RA were treated with intravenous infliximab (3mg/kg) in combination with methotrexate (MTX) (10-20mg). IgG was purified from their serum by caprylic acid. Analysis of IgG glycosylation was performed by lectin blotting/immunoblotting and enzyme linked lectin assay (ELLA)/enzyme linked immunosorbent assay (ELISA) using the Griftonia (bandeiraea) simplicifolia lectin II and protein -A/alkaline phosphatase. The purity of IgG samples obtained was higher than 90%.The sensitivity of the lectin/immunoblotting method was of about 0.25 mu g of IgG. The inter- and intraassay coefficients of variation (CV) were 1.3% and 9.0% for lectin blotting, and 4.6% and 8.3% for immunoblotting, respectively. The sensitivity of the ELLA/ ELISA approach was 0.025 mu g/mu L and the inter- and intraassay CV were 6.2% and 7.7% for ELLA, and 5.1% and 14.1% for ELISA, respectively. A good linear correlation (r(2)=0.18, P < 0.05) was obtained between the two different experimental approaches. A decrease of GO was observed in patients who clinically improved (according to the American College of Rheumatology criteria) following the pharmacological treatment. Our data indicate that infliximab can reduce the concentration of GO in patients with active RA.