TNF and chronic obstructive pulmonary disease: The down-regulation of TNF-α, IL-6, and IL-17 secreted by alveolar macrophages in COPD rats was similar to that in dexamethasone group (P = 0.324; P = 0.208; P = 0.957), but the comparison of IL-1β had a statistical difference (P < 0.001) (Fig. 6).