Many organisms use antimicrobial peptides to fend off microbial pathogens. These gene-encoded, ribosome-synthesized peptides are among the major effectors of innate immunity, an ancient defense system present in all multicellular organisms. In an Advanced Online Publication in Nature, Nita Salzman and colleagues at the Medical College of Wisconsin, Wisconsin, US, provide direct evidence of the crucial role of antimicrobial peptides in mammalian host protection and envision new therapeutic applications for these molecules (Nature, 10.1038/nature01520, March 19, 2003).

Salzman et al. genetically modified mice to produce defensin HD-5, a human intestinal antimicrobial peptide. Mice endogenously synthesize defensin-related peptides, termed cryptdins. Transgenic mice challenged with orally administered Salmonella typhimurium, a murine enteric pathogen that is less sensitive in vitro to the bactericidal activity of cryptdins than to HD-5, were markedly resistant to salmonellosis compared to wild-type mice.

Susceptibility of each animal species to a particular...

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