The standard dual classification of macrophages postulates that M1 macrophages that differentiate in response to proinflammatory cytokines (e.g., interferons and tumor necrosis factors) are involved in antitumor activities, whereas M2 macrophages that differentiate in response to immunomodulatory signals [e.g., IL-4, IL-10, and transforming growth factor–β (TGF-β)] are associated with tumor promotion (55). This evidence concerns the gene IL4 and neoplasm.