C2 and viral infectious disease: Differential gene expression analysis between bronchiole clusters revealed downregulation of several genes in the NACE2i-treated group including C2 of the complement cascade and DnaJb1 and DnaJb4 (DnaJ heat shock protein family (Hsp40) member B1 and B4), which are involved in virus replication, hyperinflammation, and tissue damage during viral infections (Fig. 3d).