Mirella Profita from the Institute of Biomedicine and Molecular Immunology “Alberto Monroy” in Palermo, Italy, and colleagues showed that lung secretions from people with COPD and those who smoke cigarettes have higher levels of interleukin-17A and thymic stromal lymphopoietin (TSLP), two proteins associated with inflammatory immune responses, than samples from healthy non-smokers. Here, IL17A is linked to chronic obstructive pulmonary disease.