CD4 and pulmonary emphysema: There is usually a higher level of eosinophils in peripheral blood and airways, higher CD4+/CD8+ T cells in the airway mucosa, thicker epithelial basement membrane, higher diffusing capacity, higher exhaled nitric oxide, lower high-resolution computed tomography scan emphysema score, and greater reversibility to bronchodilator in ACO.21 There is also a greater response to treatment with steroids in ACO which makes it pertinent to identify patients with ACO for early inclusion of inhaled steroids (ICS) to the bronchodilator treatment.24,7,25