NETs are composed primarily of eDNA (free DNA), neutrophil elastase (NE), myeloperoxidase (MPO), histones, and granules (Brinkmann et al., 2004) and are involved in several inflammatory diseases of the lungs, such as chronic obstructive pulmonary disease (COPD) and acute lung injury (Jorch and Kubes, 2017; Söderberg and Segelmark, 2018). Here, MPO is linked to chronic obstructive pulmonary disease.