Fig. 3
From: Role of mast cells in the pathogenesis of severe lung damage in COVID-19 patients
Mast cells in the lung tissues of COVID-19 patients. A–C Immunohistochemical staining with mouse monoclonal antibodies to tryptase (Abcam, # ab2378, dilution 1:4000) in accordance with standard protocol; D–F Immunohistochemical staining with mouse monoclonal antibodies to chymase (Abcam, #ab233103, dilution 1:1000). The peroxidase label on antibodies was visualized using DAB as a substrate (Vector Laboratories, Burlingame, CA, USA). The slices contrasted with Mayer’s hematoxylin. A, B Early diffuse alveolar injury, mast cell tryptase expression; mast cells are unevenly distributed in the alveolar septa. C Early diffuse alveolar damage, active degranulation of MCs, arrow indicates mast cell at the end of degranulation. D, E Uneven distribution of MCs with chymase expression. F Pronounced degranulation of mast cell chymase (arrows) with alveolar damage in the late stage. Scale bars A—100 μm, others—50 μm