Anti-CCP2 IgG was efficiently purified from plasma and synovial fluid. Schematic illustration of the anti-CCP2 IgG purification process. (A) Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by Coomassie staining of different protein fractions collected during the anti-CCP2 IgG purification process is shown. Representative samples from plasma (B) and synovial fluid (C): molecular marker (lane 1); plasma/precipitated synovial fluid proteins (lane 2); protein G column flow through (lane 3); protein G column IgG eluate, before dialysis and filtration (lane 4); protein G column IgG eluate, after dialysis and filtration (lane 5); CCP2 column IgG flow through (lane 6); CCP2 column anti-CCP2 IgG eluate (lane 7). Lanes 2 and 3: 15 μg/well. Lanes 4 to 7: 5 μg/well. IgG, immunoglobulin G; PBS, phosphate-buffered saline.