Clinical observations also confirm the pathogenetic role of NETs in CF, by revealing a positive correlation between the impairment of respiratory function and the level of free DNA or elastase in CF airways, or the level of MPO and antibodies to PAD4 in circulating blood (Marcos et al., 2015; Dittrich et al., 2018; Yadav et al., 2019). The gene discussed is PADI4; the disease is cystic fibrosis.