CCL17 and chronic obstructive pulmonary disease: In our study, CSE/PPE induced an increase in NETosis (Figure 4o), MMP-9, IL-6, TNF-α, IL-1β, MIP-2, KC, RANTES, MCP-1, MDC, TARC, and eotaxin levels in the BALF, inflammatory cell infiltration, luminal occlusion by secretion of mucous glycoproteins and inflammatory exudates, airway wall thickness, mucus hypersecretion, alveolar enlargement, and alveolar destruction (Figure 5a), as observed in the lung tissues of the COPD group.