Alpha-1 antitrypsin (AAT) is the most abundant serine protease inhibitor circulating in the blood. AAT deficiency (AATD) is an autosomal codominant condition affecting an estimated 3.4 million individuals worldwide. The clinical disease associated with AATD can present in a number of ways including COPD, liver disease, panniculitis and antineutrophil cytoplasmic antibody vasculitis. AATD is the only proven genetic risk factor for the development of COPD, and deficient individuals who smoke are disposed to more aggressive disease. Principally, AAT is a serine protease inhibitor; however, over the past number of years, the assessment of AAT as simply an antiprotease has evolved, and it is now recognized that AAT has significant anti-inflammatory properties affecting a wide range of cells, including the circulating neutrophil.