Freshly isolated left lung (pulmo sinister) were fixed with 4% formaldehyde, embedded in paraffin, and cut in 5-μm-thick sections. TUNEL stain (Promega) was performed according to manufacturer's protocol. For eosin and haematoxylin staining, deparaffinised, rehydrated slides were stained for 4 min with haematoxylin (Morphisto), rinsed for 4 min with tap water, stained for 30 s with eosin Y (Sigma-Aldrich), and finished by dehydration with ethanol and xylol. For immunofluorescence, lungs were deparaffinised and rehydrated; target retrieval was performed using Dako target retrieval solution. Sections were blocked with 2% bovine serum albumin, 0.5% fish gelatin, and 0.3% Tween-20 for 90 min, followed by blocking with mouse-on-mouse IgG blocking solution (Thermo Fisher), if anti-Nsp9 was used. Primary antibodies were Nsp9 (2C6.H1; Thermo Fisher), cleaved caspase 3 (5A1E; Cell Signaling), CD68 (FA-11; Bio-Rad), and CD11c (N418; BioLegend). Primary antibodies were incubated overnight at 4°C and corresponding secondary antibodies for 2 h at room temperature. All images were scanned on an automated tissue FACS microscopy stage on an Observer Z1 microscope at ×20 magnification (NA 0.5). Automated analysis was performed with CellProfiler [22 (link)].