In pulmonary fibrosis, both alveolar macrophages (CD11b low CD11c++ CD169+) and interstitial macrophages (CD11b+ CD11clow CD169−) can differentiate into M1 and M2; moreover, the chemotactic monocytes are also the precursors of M1 and M2 (30, 31). This evidence concerns the gene SIGLEC1 and pulmonary fibrosis.