In humans, four a-defensins, human neutrophil peptides 1-4 (HNP [1] [2] [3] [4] , are expressed in neutrophils and monocytes of myeloid lineage, and a-defensins (HD5 and HD6) are produced primarily in Paneth cells of the small intestine. In neutrophils, HNP 1-4 are stored in the cytoplasmic azurophil granules which are mobilized during phagocytosis resulting in the exposure of ingested microorganisms to high concentrations of HNPs in the phagolysosomes [2] . In the setting of bacteremic sepsis, HNPs also accumulate in the extracellular compartment [15, 16] . Several studies have demonstrated an extracellular role for myeloid adefensins in regulating cellular activities including cell proliferation [17, 18, 19] , neovascularization [20, 21] , chemotaxis [22] , and regulation of cytokines [23, 24] and signal transduction pathways [17, 19, 24, 25] . To date, these activities have been attributed to the mature, folded a-defensin.