MUC5AC and inflammatory response: Elevated mucin MUC5AC concentration in sputum (when measured with MUC5B) directly associates with disease severity, exacerbation frequency, and lung function decline; microbiome analysis reveals increased abundance of Proteobacteria and Haemophilus genera, closely linked to mucus plug formation and severity (175); inflammatory marker testing shows upregulated MMP-9, LTB4R, and A1AR mRNA, while CC16 mRNA is significantly reduced—the latter particularly associating with impaired lung function and eosinophilic inflammation.