IFNG and pulmonary emphysema: In addition, various cytokines (e.g. IL-1β, IL-6, TNF-α, IFN-γ), growth factors (e.g. EGF, GMC-SF, TGF-β), and chemokines (e.g. CCL2, CXCL1, CXCL8, CXCL9, CXCL10, CXCL11) may be involved in the development of pulmonary inflammation, emphysema, and fibrosis around small airways in COPD [6].