The concentrations of CXCL1, IL-4, IL-13, IL-6 and IL-17 in the plasma were significantly higher in patients with IPAF compared with IIP and the normal cohorts, but no significant difference in the plasma levels of interferon-γ (IFN-γ) was found in the patients with IPAF, IIP, COPD and healthy controls (Fig. 2). Here, IL17A is linked to chronic obstructive pulmonary disease.