Specimens were immediately fixed in 10% formalin for 24 to 72 hours, embedded in paraffin, and sectioned at a thickness of 5 μm. Sections were stained with hematoxylin and eosin, trichrome, or appropriate antibodies for immunohistochemistry and then examined under light microscopy. Additional adjacent tissue specimens were immediately placed in storage buffer (MACS Tissue Storage Solution, Miltenyi Inc.) and then digested in an enzymatic cocktail [collagenase I/dispase II (1 μg/ml) tissue or Miltenyi Multi Tissue Dissociation Kit] using a gentleMACS Octo Dissociator (Miltenyi Inc.), as previously described (69 (link)). For lungs 2, 3, and 4, homogenates were serially filtered through sterile gauze, 100- and 40-μm sterile filters (Thermo Fisher Scientific) to generate single-cell suspensions, which were frozen immediately in 90% fetal bovine serum/10% dimethyl sulfoxide and stored at −80°C for subsequent batched flow cytometric analysis. Lung 1 homogenates were used for protocol refinement, and insufficient cells were available for inclusion in flow cytometric analysis.