PA28γ serum levels measured by sandwich ELISA in patients with rheumatoid arthritis treated with Abatacept. A) Correlation analysis of PA28γ level in sera of 13 RA patients at three time points of serum withdrawal. PA28γ level were compared with disease activity score 28 (DAS28) (r = 0.319, P = *0.047, left), erythrocyte sedimentation rate (ESR) (r = 0.446, P = **0.005, middle) and C-reactive protein (CRP) (r = 0.006, P = 0.971, right). B) Course of PA28γ level in Abatacept treated patients with RA. Serum withdrawal was done at indicated time points and the results are represented as mean PA28γ levels of duplicate wells. C) Graphical presentation of PA28γ serum level, DAS28 (upper diagrams) and ESR (lower diagrams) of three abatacept treated patients. Black diamonds correspond to PA28γ levels and white rectangles to DAS28 and ESR.