Endogenous antimicrobial peptides are widely distributed among vertebrates. Most are amphiphilic, polycationic molecules with an α-helical, cystine-stabilized β-sheet, or proline-rich structure. Secreted and cell-associated antimicrobial peptides enable their hosts to resist incursions by potential pathogens. Such peptides present a series of barriers to the pathogens, to evade or overcome. In humans (and other mammals), defensins and cathelicidins are the principal antimicrobial peptides of neutrophils and epithelial cells. Many mucosal surfaces are bathed by antimicrobial proteins, including lysozyme, lactoferrin, secretory leukoprotease inhibitor (SLPI), and secretory phospholipase A2. All defensins have largely β-sheet structure and contain three intramolecular cystine disulfide bonds. The smallest, .-defensins, are circular peptides that contain 18 residues, α-defensins have between 29 and 35 residues, and β-defensins have up to 45. Defensins are effective broadspectrum microbicides, especially when present in high local concentrations or acting in low-ionic strength media. High local concentrations occur within phagolysosomes, in the capillary-like lumen of small intestinal crypts, and at interfaces between effector and target cells.
ASJC Scopus subject areas
- Immunology and Microbiology(all)