MPO and dermatitis: The luminol-dependent bioluminescence signal has been demonstrated to be dependent on myeloperoxidase in vitro, and in vivo in a mouse model of dermatitis.8 Myeloperoxidase is the most abundant protein component of the azurophilic granules of neutrophils and is present in the lysosome of monocytes.22 Neutrophils and inflammatory monocytes have been identified in inflamed eyes in the mouse models of EIU19 and EAU23 by flow cytometry and in the rat model of PMU14 by immunohistochemistry.