Defensins are a family of antimicrobial and cytotoxic peptides thought to be involved in host defense. They are abundant in the granules of neutrophils and also found in the epithelia of mucosal surfaces such as those of the intestine, respiratory tract, urinary tract, and vagina. Members of the defensin family are highly similar in protein sequence and distinguished by a conserved cysteine motif. Several of the alpha defensin genes appear to be clustered on chromosome 8. The protein encoded by this gene, defensin, alpha 5, is highly expressed in the secretory granules of Paneth cells of the ileum.