Neutrophilic defensins penetrate the blood‐brain barrier

AbstractDefensins are small, cationic, cyclic peptides that are abundantly stored in granules of neutrophils. Defensins non‐specifically interact with membranes by forming weakly ion‐selective pores. Here we demonstrate immunolocalization of defensin‐secreting cells in human brain. Defensins, secreted by activated granulocytes, apparently are not prevented by the blood‐brain barrier (BBB) from diffusing across cerebral endothelium to penetrate the neuropil for a considerable distance from the granulocyte. This is in contrast to other neutrophil proteins like the granuleassociated enzyme elastase or the cytosolic protein MRP‐14, which are strictly localized to the cytoplasm or granules of neutrophils. Thus, defensins, known chemokinetic and chemotactic molecules, display a unique distribution at BBB sites. © 1995 Wiley‐Liss, Inc.