Defensins: “Simple” antimicrobial peptides or broad-spectrum molecules?

Small cationic peptides highly conserved in vertebrates, both α- and β-defensins were primarily identified as anti-microbial compounds involved in innate immunity. While human α-defensins are mostly expressed by neutrophils, β-defensins are secreted by epithelial cells of the skin and mucosae. Besides their anti-microbial activity, accumulating data emerged in the past decade indicating that defensins have extended functions in human physio(patho)logy. Indeed, defensins appeared as modulators of the adaptive immune system and angiogenesis, key mediators of wound healing and determinant players in male fertility. Furthermore, the impact of defensin expression in cancer and the potential use of these small peptides as biomarkers or even therapeutic tools should not be ignored. In the present review, we describe recent research works regarding the diversified functions of defensins, by mainly focusing on human models.