MPO and Behcet disease: Immunohistochemical data showed that assessment of neutrophil infiltration by quantification of MPO-positive cell infiltration and immunoreactivity for nitrotyrosine, caspase-3, caspase-8, caspase-9, and caspase-12 with brown staining did not further increase in the aortic rings from the BD-IR group compared to the BD rats (Fig. 6).