Defensins in the oral cavity: distribution and biological role.

The oral cavity outreaches as a particular environment in which there is a continuous interplay between bacteria, fungi and viruses, and the epithelial barrier. Among the innate mechanisms that aim to establish a regulated equilibrium between health and disease, natural antimicrobial peptides, especially those part of the defensins' family, have emerged as fundamental mediators. Their biological role is emphasized by the large number of expressed genes, as well as the multiplicity of the individual molecules present on biological tissues and fluids, in physiological and pathological conditions. Furthermore, the direct antimicrobial action, defensins may play a pivotal role in the orchestration of the innate response and contribute to the interplay between the innate and adaptive immunity. This review focuses on the specificities of defensins' structure, expression and biological role in the oral environment, enlightening their relevance in physiological and pathological conditions.