TNF and chronic obstructive pulmonary disease: There is a heightened inflammatory response in the lower airways and lungs of patients with stable COPD associated with enhanced expression of a number of key cytokines including TNF-α, IFN-γ, IL-1β, IL-6, IL-17, IL-18, IL-32 and TSLP and growth factors, such as TGF-β [22, 39, 130].