By measuring klotho expression in the lungs of COPD patients and in a mouse model of ozone-induced COPD, Wei Gao et al. reported that klotho expression was reduced in the lungs of smokers and further decreased in the lungs of COPD patients, and 6 weeks of ozone exposure reduced klotho levels in airway epithelial cells (17). The gene discussed is KL; the disease is chronic obstructive pulmonary disease.