Cationic antimicrobial peptides are present throughout the plant and animal kingdoms and bear striking structural and functional similarities across species lines. They provide primitive, nonspecific means of combating a variety of bacteria, fungi, enveloped viruses, and protozoa. Some are also cytotoxic against host cells, including neoplastic cells.
Cationic antimicrobial peptides may play various roles in
inflammation and tissue repair.
Antimicrobial peptides are found in epithelial tissues regularly exposed to microbial attack as well as in cells whose primary function is defense against potential pathogens. They constitute an important part of the nonoxidative antimicrobial arsenal of leukocytes. They are preformed and/or readily synthesized when the cells are stimulated by exposure to pathogens. They exert their effects directly by inserting into membranes of target cells and forming
ion channels which increase membrane permeability; however,
antimicrobial peptides can also act as
opsonins to facilitate phagocytosis. Resistance to
defensins is a
virulence factor for organisms such as Salmonella sp. The study of
cationic antimicrobial peptides is increasing our understanding of innate immunity,
inflammation, and the pathogenesis of
genetic diseases such as specific granule disease in humans. Therapeutic applications of
antimicrobial peptides are currently under investigation.