Human neutrophil alpha-defensins (Human Neutrophil Peptides, HNP) belong to the family of cationic
trisulfide-containing microbicidal peptides. Three highly homologous human defensins stored in
azurophilic granules of polymorphonuclear leukocytes (PMN), HNP 1-3, account for about 5% of total
PMN protein and comprise about 99% of the total defensin content of the neutrophils with traces of
HNP-1, HNP-2 and HNP-3 are encoded by two genes DEFA1 and DEFA3 localized to chromosome 8.
Number of gene copies substantially varies between individuals with complete lack of the DEFA3 allele
in 10% subjects. DEFA1 and DEFA3 encode identical peptides except the conversion of the first amino
acid from alanine in HNP-1 to aspartic acid in HNP-3; HNP-2 represent N-terminally truncated iso-form
lacking the first amino acid.
HNP 1-3 are capable to kill and/or inactivate a broad spectrum of bacteria, fungi or some enveloped
viruses and have recently been shown to exert the anti-HIV activity produced by CD8+ T cells of HIVnonprogressors.
HNP 1-3 have the potential to modulate immune response and inflammation by
inducing the chemokine interleukin-8 (IL-8) in epithelial cells and modulating cytokine expression in
several cell types and causing chemotaxis to monocytes, T cells and immature dendritic cells.
Defensins are relatively resistant to proteolysis, low pH and boiling. Activation of neutrophils leads to
rapid release of HNP. HNP can be measured in plasma and other body fluids during infection and
inflammation. Micromolar concentrations of HNP are described in septic blood, while in normal plasma
very low levels of HNP are present. (HNP 1-3 can be measured using Human Neutrophil Defensin 1-3
(HNP 1-3) ELISA, Cat. # HK317).
Natural human neutrophil defensin 1-3 can be used for functional studies in vitro. Natural HNP is tested
for three major bioactivities described for human alpha-defensins, microbicidity, suramine-sensitive
induction of interleukin-8 in bronchial epithelial cell line A-549 and mammalian cell cytotoxicity. In all
bioassays performed, HNP showed high bioactivity comparable with those described in cited
references. Please pay attention to the fact that HNP are highly cationic and adsorptive to other proteins
and substances which can modulate the bioactivity of HNP.
For testing of biological activity of HNP in vitro dilutions have to be made according to published
references. Users should test the reagent and determine their own optimal concentrations. It is
recommended to use adequate dilution of 0.01% acetic acid in solvent.
Handle natural HNP according to guidelines for preventing transmission of blood-borne infections.