Eosinophils are the main IL-25–producing cells in the blood. (A-B) Flow cytometric analysis of intracellular production of IL-25 by eosinophils, neutrophils, and monocytes in an active CSS patient (A) and in all tested patients (B). (C-D) Flow cytometric analysis of intracellular production of IL-25, IL-4, and IFN-γ by T cells in an active CSS patient and a healthy donor (C) and in all tested patients (D). * P < .05; ** P< .01; *** P < .001. Histograms in each panel are representative of 3 to 5 patients in at least 3 independent experiments.