Interestingly, a recent study proposed that increased levels of interleukin-10 (IL-10) in COVID-19 lungs polarize alveolar macrophages into ACE2-expressing M2c-type macrophages that function as spreading vectors for viral infection, while depletion of alveolar macrophages in mouse models reduced SARS-CoV-2 pathogenicity (37). This evidence concerns the gene ACE2 and viral infectious disease.