Immunohistochemical localization of defensin in human coronary vessels

Neutrophil defensins comprise a family of cationic peptides that possess potent antimicrobial activity. Defensins are normally sequestered in cytoplasmic granules with their primary site of action in phagolysosomes, although some peptide is released into the circulation during the course of infection or inflammation. In view of the fact that neutrophils adhere to the endothelium and that defensins have been reported to bind to human endothelial cells in vitro, we used immunohistochemistry to study the distribution of these peptides in normal and in atherosclerotic human coronary arteries. Defensin was found primarily in the intima of normal and atherosclerotic vessels, most prominently in association with intimal smooth muscle cells. Both large- and small-vessel endothelium stained focally for defensin. Defensin was also found in the media near the external elastic lamina and in some periadventitial vessels. The same distribution was seen in vessels that had been perfusion fixed immediately upon procurement, excluding diffusion of defensin from PMNs ex vivo. These data indicate that neutrophil defensin is present in the walls of human coronary arteries. The deposition of defensin in vessels may contribute to the pathophysiological consequences of inflammation in addition to their role in host defense.