IL‐33 promotes M2 macrophage polarization via ornithine decarboxylase (ODC) activation. A, IL‐10, TGF‐β and IL‐12p35 protein levels were determined by Western blot in IL‐33–induced M2 macrophage with or without knocking down ODC. B, Immunofluorescence staining for IL‐33–induced M2 macrophages with or without knocking down ODC. The red signal represents the staining of ODC, and the green signal represents the staining of ARG1 (scale bar = 20 μm). C, The expression of CD80 (M1) and CD206 (M2) by flow cytometry in IL‐33–induced macrophages with or without knocking down ODC. D, Determination of polyamines in IL‐33–induced M2 macrophage supernatants with or without knocking down ODC by HPLC. E, iNOS and ARG1 protein levels were determined by Western blot in IL‐33–induced M2 macrophage with or without knocking down ODC. *P < .05; **P < .01; ***P < .001. Bars indicate mean and SEM of triplicate experiments and show a representative experiment of at least 3 independent experiments performed for each panel