Endogenous vertebrate antibiotics. Defensins, protegrins, and other cysteine-rich antimicrobial peptides.

Although newly recognized, endogenous cystine-stabilized beta-sheet antimicrobial peptides have ancient origins. These peptides can arm circulating phagocytes and cells of the gastrointestinal, respiratory, and genitourinary tracts to resist invasion by bacteria, mycobacteria, fungi, and enveloped viruses. Defensins and protegrin-like peptides are likely to play a considerable role in innate immunity and may provide molecular templates that can be used to generate novel antibiotics for topical and systemic use.