Concentrations of IL-17C were significantly increased during advanced COPD (GOLD III/IV) compared to moderate (GOLD I/II) COPD, whereas concentrations of IL-17A, IL-17E, IL-8, and CXCL5 did not associate with disease severity (Fig 6A and Table 2). This evidence concerns the gene CXCL8 and chronic obstructive pulmonary disease.