Macrophage subsets have distinctive inducers and multiple functions. Macrophages polarise into M1 subset under the influence of IFN- and LPS and have antitumour functions via the secretion of effective factors such as iNOS, IL-1, TNF, and IL-6. In contrast, IL-4 and IL-13 stimulate M2a polarisation; M2b is induced by exposure to TLR and IL-1R, and IL-10 is described as an inducer of M2c. The three M2 subtypes are described as tumour promoters; they induce tumour growth through inhibition of efficient factors and/or overexpression of tumour progression factors such as IL-10, TGF-, and angiogenesis mediators.
