MUC5AC and inflammatory response: We selected highly differentiated Scgb1a1-expressing small human airway epithelial cells (hSAECs) for this study because hSAECs are a site of RSV replication in LRTI (46); inhibition of the innate pathway in this cell type in vivo blocks RSV-induced airway inflammation and airway obstruction (6); and, Scgb1a1+ hSAECs produce pathogenic mucin- and T helper 2 lymphocyte-activating cytokines that mediate disease (47).