IL-10 promotes mast cell homeostasis and differentiation towards a mucosal mast cell phenotype

We recently demonstrated an unexpected role for IL-10 in driving mast cell (MC) activation and proliferation.  IL-10 stimulation significantly enhanced IgE-mediated MC activation, upregulated FceRI expression, and promoted MC-mediated food allergy. Surprisingly, IL-10 also amplified cytokine production in un-activated MCs and enhanced their proliferation and survival, suggesting a role for IL-10 in MC homeostasis. Herein, we demonstrate that IL-10 can significantly expand MC proliferation and activity during homeostatic conditions. Treatment with IL-10 enhanced the proliferation and survival of both IL-3 and IL-3+SCF cultured bone marrow-derived MCs (BMMCs). This corresponded with a dramatic increase in cytokine production in IL-10-treated cells, along with upregulation of FceRI expression. While SCF was dispensable for the increased FceRI, it significantly enhanced cytokine production compared to cells cultured in IL-3 alone. Further analysis revealed a distinctive mucosal MC phenotype in IL-10-treated cells, characterized by beta7-integrin expression and enhanced secretion of murine MC protease-1. Lastly, autocrine IL-10 also supported MC expansion and function, as blocking IL-10 signaling attenuated MC expansion, inducing apoptosis, and decreasing cytokine production. Taken together, these data suggest an important role for IL-10 in maintaining MC responses during physiological conditions.