What cytokine milieu promotes macrophage activation versus anti-inflammatory responses?

• A. IL-4 activates neutrophils
• B. TNF-α suppresses macrophages
• C. IFN-γ and TNF-α promote macrophage activation (M1); IL-4 and IL-10 promote anti-inflammatory/M2 phenotypes.
• D. IL-10 alone activates macrophages

Answer: (C)

Macrophage behavior is shaped by the surrounding cytokines, guiding them toward a pro-inflammatory, microbicidal state (M1) or an anti-inflammatory, tissue-repair state (M2). IFN-γ, especially with TNF-α, drives classical activation, enhancing microbicidal functions and producing pro-inflammatory mediators. In contrast, IL-4 and IL-10 push macrophages toward the anti-inflammatory/M2 phenotype, supporting tissue repair and dampening inflammation. So, a milieu with IFN-γ and TNF-α activates macrophages in a pro-inflammatory way, whereas IL-4 and IL-10 promote anti-inflammatory/M2 responses. The other statements don’t fit: IL-4 is not an neutrophil activator; TNF-α does not suppress macrophages; IL-10 alone does not activate macrophages.