IL-10 inhibits the synthesis of migration inhibitory factor and migration inhibitory factor-mediated macrophage activation.

IL-10, in addition to being a cytokine synthesis-inhibitory factor, is a cytokine that exerts multiple effects on various cell types. Recombinant human migration inhibitory factor (MIF) inhibits the migration of human monocytes as well as that of guinea pig and murine macrophages. In addition, it has recently been shown to activate human monocyte-derived macrophages to suppress the growth of and/or kill both intracellular parasites and extracellular tumor targets in vitro and to have adjuvant activity in vivo. In this study, we examined the interactions between IL-10 and rMIF. We demonstrate that IL-10 reduces the production of MIF from T cells and abolishes rMIF-mediated migration inhibition of human monocytes. Incubation of IL-10 together with rMIF diminishes rMIF-induced intracellular killing of Leishmania donovani by human monocyte-derived macrophages and inhibits nitric oxide production and nitric oxide synthase activity by murine macrophages.