We next used our previous human RV challenge studies (1, 15) to more accurately define the temporal dynamics of mucin expression during RV-induced COPD exacerbations (study is outlined in Figure 2A and Supplemental Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/JCI120901DS1). This evidence concerns the gene MUC5AC and chronic obstructive pulmonary disease.