M1/M2 Macrophage Polarization

M1/M2 polarization describes two broad functional states of macrophage activation. M1 macrophages, activated by IFN-γ and bacterial lipopolysaccharide, are pro-inflammatory and associated with anti-tumor activity, producing cytokines such as IL-1β, IL-6, and TNF-α. M2 macrophages, activated by IL-4 and IL-13, are anti-inflammatory and associated with tumor promotion — supporting angiogenesis, immune suppression, and metastasis while secreting molecules such as IL-10 and TGF-β.

These states represent ends of a continuum rather than fixed categories, and tumor-associated macrophages (TAMs) can express a range of intermediate or context-dependent phenotypes.