TGFB1 and pulmonary fibrosis: Macrophages are also important cells in the development of pulmonary fibrosis as they produce large amounts of IL-8, which is an important chemotactic pair for neutrophils, and contributes to pulmonary fibrosis by producing PDGF and TGF-β, and inducing fibroblasts and myofibroblasts to produce extracellular matrix [49].