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. The gene discussed is CD8A; the disease is pulmonary emphysema.