IMMUNOHISTOCHEMICAL LOCALIZATION OF DEFENSIN IN HUMAN CORONARY VESSELS

Neutrophil defensins comprise a family of cationic peptides that posse ss potent antimicrobial activity. Defensins are normally sequestered i n cytoplasmic granules with their primary site of action in phagolysos omes, although some peptide is released into the circulation during th e course of infection or inflammation. In view of the fact that neutro phils adhere to the endothelium and that defensins have been reported to bind to human endothelial cells in vitro, we used immunohistochemis try to study the distribution of these peptides in normal and in ather osclerotic human coronary arteries. Defensin was found primarily in th e intima of normal and atherosclerotic vessels, most prominently in as sociation with intimal smooth muscle cells. Both large- and small-vess el endothelium stained focally for defensin. Defensin was also found i n the media near the external elastic lamina and in some periadventiti al vessels. The same distribution was seen in vessels that had been pe rfusion fixed immediately upon procurement, excluding diffusion of def ensin 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 consequen ces of inflammation in addition to their role in host defense.