Induction of macrophage TNF-α production by T cells from synovial membranes in rheumatoid arthritis (RA-Ts) is dependent on phosphatidylinositol 3-kinase (PI3K). RA-Ts were added in co-culture with macrophages primed with macrophage-colony-stimulating factor at a RA-T:macrophage (T:M) ratio of 5:1 in the presence or absence of the PI3K inhibitor wortmannin (50 nM) or the p70S6K inhibitor rapamycin (1 nM) for 24 hours at 37°C/5% CO2, after which supernatants were harvested and stored at –20°C until ELISA. Bars represent mean TNF-α of triplicate culture supernatants ± SD, for a representative of N = 2 replicate experiments. Macros = macrophages; Rapa. = rapamycin; T:M = ratio of RA-Ts to M-CSF-primed macrophages; TNF = tumour necrosis factor; Wort. = wortmannin. **P < 0.01.