CXCL8 and chronic obstructive pulmonary disease: We found that the levels of IL-6, IL-8, TNF-α, and IFN-γ in the smoker and COPD III-IV groups were significant higher than those in the non-smoker and COPD I-II groups, and TLR2 in mononuclear cells of the peripheral blood was significantly correlated with the clinical classification of the patients (Figs. 3A–3E).