Gene-encoded peptide antibiotics and innate immunity. Do 'animalcules' have defence budgets?

Gene-encoded peptide antibiotics have been isolated from plants, animals and microbes. Their protective role has been related to innate immunity, which has gradually become accepted across the biomedical community. The evidence for the immune function of peptide antibiotics has been convincingly demonstrated by a combination of both in vitro and in vivo data for plants and insects, but for vertebrates in vivo data are scarce. Using frogs as model systems, it has been shown that the genes for antibacterial peptides are down-regulated by glucocorticoids, while IkappaB alpha is clearly up-regulated. Experimental infections with frog bacteria have shown that the normal capacity to control the natural flora is lost after treatment with glucocorticoids. A low-specificity immune mechanism is cost-effective, something that may have been of importance during animal evolution.