T cells from synovial membranes in rheumatoid arthritis (RA-Ts) induce production of IL-10 by monocytes and macrophages. RA-Ts were co-cultured with resting monocytes (a) or M-CSF-primed macrophages (b). Bars show mean IL-10 in triplicate culture supernatants ± SD, for a representative of N = 3 replicate experiments. Macros = M-CSF-primed macrophages; M-CSF = macrophage-colony-stimulating factor; Monos = monocytes; T:M = ratio of RA-Ts to (panel a) monocytes or to (panel b) M-CSF-primed macrophages. *P < 0.05, **P < 0.01, ***P < 0.001.