TGFB1 and pulmonary fibrosis: Since the master regulator of organ fibrosis, TGF-β, was shown to be highly expressed in both SARS-CoV-2-infected lung tissues and classical pulmonary fibrotic lung tissues, we analyzed the TGF-β expression on macrophages, fibroblasts and type II alveolar epithelial cells (AEC2), which are widely accepted as key effector cells that generate TGF-β in idiopathic pulmonary fibrosis.30 TGF-β was found mainly expressed on infiltrated macrophages and fibroblasts in both SARS-CoV-2-infected hCD147 mice at 13 d.p.i.