Cytokine secretion in MS-, ES, IT- and T-MPCs. IL-6, IL-8, IFN-γ and TGF-β were constitutively secreted and easily exceeded 1 pg/ml under standard culture conditions. However, IL-2, IL-4, IL-5, IL-10, IL-13 and TNF-α were secreted less than 1 pg/ml or not detected. MS-, ES-, IT- and T-MPCs upon stimulation secreted a large amount of IL-6, IL-8, IL-10 and TGF-β. The expression of IL-6 and IL-10 were significantly higher in the ES-MPCs than MS-, IT- and T-MPCs. Data are expressed as the mean ± SEM. *, ǁ, ¶, **, ‡‡‡, §§§, ǁǁǁ P = 0.001, † P = 0.009, ‡, §§, ¶¶, ¶¶¶ P < 0.001, § P = 0.006, †† P = 0.003, ‡‡ P = 0.004, ǁǁ P = 0.006, *** P = 0.042, ††† P = 0.046. ES, ethmoid sinus; IT, inferior turbinate; MPCs, mesenchymal progenitor cells; MS, maxillary sinus; T, tonsil.