CXCL8 and cystic fibrosis: Genes whose reduced expression associated with lower %SO, indicating less severe disease, included genes that are known biomarkers of CF airway disease such as IL-8 (CXCL8) and TNF-α (TNF) and candidate biomarkers such as CD14, CEACAM3, TGFB1, and TLR4 previously identified in the lower airways (50–52).