a, Diffuse infiltration of macrophages (red arrow) in the expanded alveolar septa in HB-01-infected hACE2 mice at 3 and 5 dpi. b, Many T lymphocytes (red arrow) infiltrated the thickened alveolar septa in the first row of b at 5 dpi in the HB-01-infected hACE2 mice. A few B lymphocytes (red arrow) were observed in the HB-01-infected hACE2 mice. Scale bars, 40 μm. Data in a, b are representative of three independent experiments.