Interleukin-10 induces apoptosis in developing mast cells and macrophages

Interleukin (IL)-10 is a potent immunoregulatory cytokine capable of inhibiting the inflammatory response. As mast cells and macrophages are central effectors of inflammation, we investigated the effects of IL-10 on mast cell and macrophage development from mouse bone marrow progenitors. Bone marrow cells were cultured in IL-3 + stem cell factor (SCF), giving rise to mixed populations of mast cells and macrophages. The addition of IL-10 greatly decreased the expansion of bone marrow progenitor cells through a mechanism requiring signal tranducer and activator of transcription-3 expression. The inhibitory effects were a result of the induction of apoptosis, which occurred with caspase-3 activation and reduced mitochondrial membrane potential. Supporting a role for the mitochondrion, bone marrow cells from p53-deficient or Bcl-2 transgenic mice were partly resistant to the effects of IL-10. Further, IL-10 decreased Kit receptor expression and inhibited survival signaling by SCF or IL-3. These data indicate that IL-10 induces an intrinsic, mitochondrial apoptosis cascade in developing mast cells and macrophages through mechanisms involving blockade of growth factor receptor function. The ability of IL-10 to inhibit survival could support immune homeostasis by dampening inflammatory responses and preventing chronic inflammation.