SERPINA1 and alpha 1-antitrypsin deficiency: Alpha1-antitrypsin inhibits neurophil elastase, and the discovery of alpha1-antitrypsin deficiency (AATD) and its association with emphysema and COPD helped to establish the concept that an imbalance between proteases and antiproteases, exacerbated by exposure to cigarette smoke, can play a key role in the development of disease, at least in a subset of COPD [2].