In the serum of COPD patients and in bronchial biopsies of asthma patients, the expression of TGF-β1 is increased (143), while the expression levels of TGF-β1 observed in both bronchial epithelial cells and alveolar macrophages of COPD patients are decreased compared to control groups (107). Here, TGFB1 is linked to chronic obstructive pulmonary disease.