Defensins are a family of variably cationic 3-5 kDa peptides with a conserved motif of six disulfide-linked cysteines. They are expressed in host defense settings (in phagocytes and epithelia) and display a broad spectrum of antimicrobial activity. The production of many defensins is constitutive but others are induced by infectious or inflammatory stimuli. Some defensins are chemoattractant for monocytes, lymphocytes, and dendritic cells.