Green et al. (2004) have reported elevated MPO immunoreactivity and activity in the cortices of AD patients, along with increased prevalence of its oxidation products. However, MPO expression in that study was attributed to neurons. Reynolds et al. (1999) detected MPO expression in CD68 expressing cells surrounding amyloid-β plaques, therefore attributing it to microglia/macrophages. More recently, MPO expression was reported in association with amyloid-β plaques in the brains of AD patients (Gellhaar et al., 2017). This evidence concerns the gene CD68 and Alzheimer disease.