MPO and type 1 diabetes mellitus: Levels of neutrophil elastase (NE) and proteinase 3 (PR3) serine proteases from neutrophil granules, involved in microbial clearance and immune regulation during inflammation, are elevated in T1D patients, as well as myeloperoxidase (MPO, an enzyme essential for microbial killing) [32] and correlate with titer and number of β-cell specific autoantibodies [33].