MPO and idiopathic pulmonary fibrosis: ,22,23,24,25 Additionally, NET-derived proteins such as histones and myeloperoxidase (MPO) have been found to be cytotoxic to alveolar epithelial cells,19 and NETs have been shown to induce lung fibroblast proliferation and differentiation,16,17 further supporting the role of neutrophil-derived NETs in lung injury and fibrosis in IPF.