Defensin antimicrobial peptides in the oral cavity

Epithelial surfaces are the most important route of entry of microbial pathogens. The interaction between bacteria and epithelial cells is now recognized to be a process in which the epithelial cells are active participants. This epithelial response is especially important in the oral cavity in which there is continual exposure to bacteria, fungi, and viruses. Humans have many mechanisms that are responsible for keeping the balance between health and disease in this complex environment. These include the natural defenses of saliva and the host innate immune responses, as well as the ability to generate antibodies via acquired immune responses. This brief review will focus on a recently recognized group of antimicrobial peptides, the defensins, and mainly on the β-defensins that are expressed by epithelial cells. These peptides are part of the innate immune system; they have broad spectrum antibacterial and antifungal activity and they have properties that may serve to link innate immunity with the acquired immune system. Their role in oral health and susceptibility to disease is only now beginning to be appreciated, and many interesting questions remain to be explored.