Human Lungs Show Limited Permissiveness for SARS-CoV-2 Due to Scarce ACE2 Levels but Virus-Induced Expansion of Inflammatory Macrophages

Spectral microscopy, single-cell/-nucleus RNA sequencing or ACE2 ‘gain-of-function’ experiments were applied on infected human lung explants and adult stem cell-derived human lung organoids to correlate ACE2 and related host factors with SARS-CoV-2 tropism, propagation, virulence, and immune activation.