Harmful substances in cigarette smoke such as oxygen radicals, acrolein and formaldehyde can cause airway epithelial damage, and can also cause the aggregation of inflammatory cells, stimulate parietal cells to secrete IL-1β, IL-6 and other inflammatory cytokines, chemoattractant and activate neutrophils, release cytotoxic substances such as proteases, aggravate local inflammation and immune response of the airways, and eventually cause changes in the structure and function of small airways and lung tissues, leading to the occurrence and development of chronic bronchitis and emphysema [26]. Here, IL6 is linked to chronic bronchitis.