Figure 2: The phenotypic polarization of macrophages in the tumor microenvironment. Macrophages can be schematically classified into two main classes depending on their phenotypic polarization: macrophages mount M1 phenotype in response to M-CSF, INFγ, LPS and other microbial products, whereas they differentiate into M2 in the presence of TGFβ, VEGF, CCL2, M-CSF, IL-4, IL-10, IL-13, glucocorticoids and immune complexes/TLR ligands. M1 and M2 display different functions. M1 macrophages are able to trigger Th1 immune response and exert cytotoxic activity towards ingested microorganisms and cancer cells. M2 macrophages activate Th2 immune response and promote angiogenesis, tissue remodeling, and tumor progression. Refer to the text for abbreviations.