Mast cells produce interleukin-25 upon Fc epsilon RI-mediated activation.

Interleukin-25 (IL-25) is a recently described T helper 2 (T(H)2) cell-derived cytokine that belongs to the IL-17 family and induces the production of IL-4, IL-5, and IL-13 from an unidentified non-T-cell population. Here, we show that mast cells are also potent IL-25-producing cells. When bone marrow-derived mast cells were stimulated by immunoglobulin E cross-linking, IL-25 mRNA was induced within 30 minutes in a calcineurin-dependent manner, and the levels of IL-25 mRNA were comparable with those of activated T(H)2 cells. Production of IL-25 by mast cells was also detected at protein levels by immunoblotting. These results suggest that mast cells may enhance T(H)2-type immune response by producing IL-25.