Cytokine-stimulated T cells induce IL-10 production by M-CSF- primed macrophages in a contact-dependent manner. Cytokine-stimulated T cells were co-cultured with macrophages and monocytes that had been primed with M-CSF. In some co-cultures, semipermeable membranes were inserted to separate the two types of cell being incubated (indicated on the chart by 'insert'). Bars show mean concentrations of IL-10 in triplicate culture supernatants ± SD, for a representative of N = 5 replicate experiments. Macro = M-CSF-primed macrophages; M-CSF = macrophage-colony-stimulating factor; Mono = monocytes.