Dr.Charles Bevins


April 16, 2004

Defensins: Natural Antibiotics in Mammalian Host Defense

Charles L. Bevins, MD PhD
Professor of Medical Microbiology and Immunology
University of California Davis School of Medicine
One Shields Avenue, Tupper Hall, Rm 3146
Davis, California 95616-8645
Phone: (530)754-6889
Lab: (530)754-6679
FAX: (530) 752-8692

Defensins: Natural Antibiotics in Mammalian Host Defense


Have you ever wondered why a cut in your mouth rarely gets infected? The answer, in part, may lay in the protection provided by peptides that function as natural antibiotics. Mammalian epithelial surfaces, such as the mouth lining, are remarkable for their ability to provide critical physiological functions in the face of frequent microbial challenges and potential infections. The fact that these mucosal surfaces normally remain infection-free suggests that highly effective mechanisms of host defense have evolved to protect these tissues. Throughout the animal and plant kingdoms, endogenous genetically-encoded antimicrobial peptides are key elements in the response to epithelial compromise (such as cuts) and microbial invasion. In mammals, these well-characterized molecules have been named defensins and cathelicidins. A major source of these host defense molecules is circulating white cells. However, more recently it has been demonstrated that mucosal epithelial cells of the skin, respiratory, alimentary, and genitourinary tracts also synthesize and release antimicrobial peptides. Much data now support the hypothesis that these molecules are important contributors to mucosal immunity. Alterations in their level of expression or biological activity can predispose the organism to microbial infection.