Defensin

Defensins are a family of small cationic antimicrobial peptides (alpha-defensins, beta-defensins, theta-defensins) that constitute one of the major innate-immune defense systems at mucosal and epithelial surfaces. They permeabilize bacterial membranes via their cationic / amphipathic structure, producing rapid microbicidal action.

Human beta-defensin 2 (hBD-2) is one of the most-studied beta-defensins and is induced in skin, gut, and lung epithelium in response to inflammation or microbial challenge. It also has chemotactic activity for immune cells, linking innate antimicrobial defense to adaptive immunity.

Other antimicrobial peptide families studied in research include the cathelicidins (LL-37) and amphibian-derived peptides such as magainin and indolicidin, which serve as the basis for several therapeutic and cosmetic AMP candidates.