BAFF expression was significantly higher in small pulmonary artery endothelial cells, alveolar epithelial cells, and alveolar macrophages in COPD patients, while circulating BAFF concentrations were higher in patients who smoked compared to non-smokers, suggesting that BAFF was associated with impaired lung function, hypoxia severity in COPD patients (27–29). This evidence concerns the gene TNFSF13B and chronic obstructive pulmonary disease.