Inhibition of phosphatidylinositol 3-kinase (PI3K) augments TNF-α production by mononuclear cells from synovial membrane in rheumatoid arthritis (RA-SMCs). RA-SMCs were cultured in the absence (controls) or presence of the PI3K inhibitors LY294002 (a) and wortmannin (b) in 24-well plastic tissue-culture plates at 1 × 106cells/ml per well for 24 hours at 37°C/5% CO2, after which supernatants were harvested and stored at –20°C until ELISA. Bars show mean TNF-α in triplicate culture supernatants ± SD, for a representative of N = 4 replicate experiments. TNF = tumour necrosis factor. **P < 0.01, ***P < 0.001.