MPO and type 1 diabetes mellitus: In previous studies, increased circulating levels of neutrophil elastase (NE) and proteinase 3 (PR3), both serine proteinases produced by neutrophils and stored in their primary azurophilic granules, as well as increased levels of myeloperoxidase (MPO)-DNA complexes, were reported in patients with T1D (12), suggesting enhanced NET formation.