To determine the potential role of DNMT3B in macrophage polarization during pulmonary fibrosis in vivo, we subjected myeloid cell specific DNMT3B deficient mice (Dnmt3bfl/flLysMCre mice) and their littermate controls (Dnmt3bfl/fl mice) to the bleomycin-induced lung fibrosis model. The gene discussed is DNMT3B; the disease is pulmonary fibrosis.