CHOP can also induce pulmonary macrophage M2-type polarization in bleomycin-induced pulmonary fibrosis model mice, while M2-type macrophages can promote pulmonary fibrosis by secreting pro-fibrotic factors, such as TGF-β, chemokines, and MMPs24 . The gene discussed is TGFB1; the disease is pulmonary fibrosis.