T cells from synovial membranes in rheumatoid arthritis (RA-Ts) induce macrophage TNF-α production. RA-Ts were co-cultured with M-CSF- primed macrophages and incubated 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 = 3 replicate experiments. Macros = macrophages; M-CSF = macrophage-colony-stimulating factor; T:M = ratio of RA-T to M-CSF-primed macrophages; TNF = tumour necrosis factor. *P < 0.05, **P < 0.01.