SPP1 and idiopathic pulmonary fibrosis: Macrophages from patients with IPF and COVID-19 were both found to express fibrosis-associated genes including Secreted Phosphoprotein 1 (SPP1), transforming growth factor beta 1 (TGFB1), transforming growth factor beta-induced (TGFBI), legumain (LGMN), and C-C Motif Chemokine Ligand 18 (CCL18) [50].