IL13 and neoplasm: Previously classified in M1 (classically activated macrophages with anti-cancer functions) and M2 (alternatively activated macrophages with pro-tumour functions), macrophages are now grouped into four categories: M1 (IFNy/LPS), involved in inflammation, microbial killing and anti-tumour functions; M2a (IL4/IL13) involved in allergic reactions, intracellular parasite killing and matrix remodelling; M2b (immunocomplexes) associated with immunoregulation and suppression of inflammation and M2c (IL10) responsible for Treg stimulation, immunosuppression and matrix remodelling.