Considering that macrophage exhibited a more extensive distribution along airways, lung parenchyma, and bronchoalveolar lavage (BAL) fluid in COPD patients [30], we hypostasized that the elevation of the expression value of TNF-α in blood was mainly due to the extensive distribution of the macrophage population in the lung, and TNF-α gene genotypes could affect the expression of TNF-α in the lung macrophages. The gene discussed is TNF; the disease is chronic obstructive pulmonary disease.