Effect of Bid suppression on Fas-induced apoptosis of RA FLS. (a) Cultured fibroblast-like synoviocytes (FLS) from five rheumatoid arthritis (RA) patients were incubated with 1 μg/ml of anti-Fas antibody and Bid expression was assessed by western blot. A representative blot is shown. (b and c) RA FLS were either non-transfected or transfected with Bid or control small interfering RNA (siRNA). Proteins were extracted 48 hours after transfection and western blot was performed. (b) Densitometric analysis of band intensities normalized to the actin band is shown. Data are the mean (standard error of the mean (SEM)) of five different RA FLS lines. * indicates P < 0.05. (c) A representative blot is shown. (d) Forty-eight hours after transfection, RA FLS were left untreated (Basal), treated for 12 hours with 1 μg/ml anti-Fas antibody or pretreated for one hour with Wortmannine (Wort) or LY294002 (LY) before Fas stimulation. Apoptosis was determined by quantification of nucleosomal release. Results are the mean (SEM) of six different RA FLS lines. * indicates P < 0.05 versus basal; and # indicates P < 0.05 versus anti-Fas-only treatment.