Representative pre/post immunohistochemical images of 4-HNE expression and their graphical representation. (a to c) Responders. (d to f) Non-responders. T0 is time at baseline; T3 is three months after anti-TNF-α treatment. (a to b) Biologic therapy responders showed lower synovial 4-hydroxy-2-nonenal (4-HNE) expression at (b) T3 compared with their (a) T0 levels. (c) Graphical illustration of synovial 4-HNE levels at T0 and T3 (P < 0.05). (d to e) No significant 4-HNE changes were seen between (d) T0 and (e) T3 in patients who did not respond to therapy. (f) Graphical representation of synovial 4-HNE levels in non-responders at T0 and T3.