Osteopontin (OPN), a type 2 mediator protein secreted by M2 macrophages, plays multiple roles in lung fibrosis, such as stimulating TGF-β1 expression and activation, promoting fibroblast to myofibroblast differentiation, and inducing the expression of ECM proteins (93). The gene discussed is TGFB1; the disease is pulmonary fibrosis.