Combined Stimulation with the T Helper Cell Type 2 Cytokines Interleukin (Il)-4 and IL-10 Induces Mouse Mast Cell Apoptosis

Mast cells are found in connective and mucosal tissues throughout the body. Their activation via immunoglobulin E (IgE)–antigen interactions is promoted by T helper cell type 2 (Th2) cytokines and leads to the sequelae of allergic disease. We now report a mechanism by which Th2 cytokines can regulate mast cell survival. Specifically, we find that interleukin (IL)-4 and IL-10 induce apoptosis in IL-3–dependent bone marrow–derived mast cells and peritoneal mast cells. This process required 6 d of costimulation with IL-3, IL-4, and IL-10, and expression of signal transducer and activator of transcription 6 (Stat6). Apoptosis was coupled with decreased expression of bcl-x(L) and bcl-2. While this process occurred independent of the Fas pathway, culture in IL-3+IL-4+IL-10 greatly sensitized mast cells to Fas-mediated death. Additionally, we found that IgE cross-linkage or stimulation with stem cell factor enhanced the apoptotic abilities of IL-4 and IL-10. Finally, IL-3–independent mastocytomas and mast cell lines were resistant to apoptosis induced by IL-3+IL-4+IL-10. These data offer evidence of Th2 cytokine–mediated homeostasis whereby these cytokines both elicit and limit allergic responses. Dysregulation of this pathway may play a role in allergic disease and mast cell tumor survival.