SERPINA1 and lung disorder: It is a multifunctional antiprotease, a member of the serpin gene superfamily, which functions primarily to inhibit the activity of neutrophil elastase (NE) and other neutrophil proteases.1, 2 Deficiency of AAT leads to progressive lung disease, due primarily to the unopposed action of NE and other neutrophil products on the extracellular matrix in the pulmonary interstitium.