Macrophages react to a diverse range of signals by secreting cytokines and chemokines, and are found in close association with myofibroblasts.119 They can be activated by TGF-β and can be important in fibrosis.16 Classically activated macrophages (M1) secrete inflammatory cytokines, including TNF-α, IL-1 and IL-6.120 M1 also promote the differentiation of Th17 cells, which are also pro-inflammatory (see below). The gene discussed is TGFB1; the disease is fibrosis.