Several defensins are recognized, the epitope has not been further characterized. Biological functions: Various functions have been described for defensins. They are antibacterial, antifungal, chemotactic for monocytes, inhibitory for ACTH-induced corticosteroid synthesis and cytotoxic for cells. Defensins are inhibited by glucosaminoglycans (self protection for cells) and high concentrations of Calpha 2+ ions. Biochemistry: Defensins are a group of cyclic peptides containing 29-35 amino acids (MW < 3500) which tend to form aggregates. The molecules are protease resistant. The defensin content of azurophilic granules in neutrophils is approximately 30 % of the total protein. Specificity: Human: Defensin 1-3 (HNP-1 to HNP-3) in human neutrophils. Synthetic defensin-1 and -2 (Bachem, Bubendorf CH) stain also positively. Not tested with Defensin-4. A side reaction to elastin has been observed in humans. Other: not tested. Defensins have been described in rabbits (NP-1 to NP-5, NP3a = Corticostatin), and in mice (cryptodin).