Mammalian Antimicrobial Peptides; Defensins and Cathelicidins

Antimicrobial peptides (also known as host defence peptides) are an increasingly well-characterized, central component of host defence against infection. These peptides are an ancient form of innate immunity, conserved across evolution; found in animals, plants and even produced by microorganisms themselves. As antibiotic resistance becomes an ever-greater concern for our ability to treat infectious diseases, the study of antimicrobial peptides is providing new insights into the functioning of innate immunity and providing templates for the development of novel therapeutics. As knowledge of the properties of these peptides has developed, it has also become clear that, in addition to broad-spectrum direct microbicidal potential, they have modulatory effects on innate and adaptive immune processes in mammals, as well as some apparently non-immune functions. This chapter focuses on two families of mammalian peptides; the defensins and the cathelicidins, concentrating primarily on human peptides, but with reference to homologous peptides in mouse models.