 Members of the cathelicidin family of antimicrobial polypeptides are characterized by a highly conserved region (cathelin domain) and a highly variable cathelicidin peptide domain.Cathelicidin peptides have been isolated from many different species of mammals.Cathelicidins were originally found in neutrophils, but have since been found in many other cells including epithelial cells and macrophages after activation by bacteria, viruses, fungi, or the hormone 1,25-D, which is the hormonally active form of vitamin D.

The general rule of the mechanism triggering cathelicidin action, like that of other antimicrobial peptides, involves the disintegration (damaging and puncturing) of cell membranes of organisms toward which the peptide is active.