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Evidence: LowPeptideResearch ChemicalEndogenous α-defensinNeutrophil granulesNot a medicine

HNP-1

The neutrophil's own antibiotic, discovered in 1985 and now studied as a blood marker of severe illness

Human neutrophil peptide 1 is one of the alpha-defensins stored in the granules of neutrophils, the commonest white blood cells. Discovered in 1985, it kills bacteria and fungi partly by binding a cell-wall building block. In people, blood levels rise with infection and severe disease, but as a test it has had mixed results.

At a Glance Read Research →
Overview

What is it?

In 1985 researchers extracted the granules of normal human neutrophils and found three small antibiotic peptides, which they named human neutrophil peptides 1, 2 and 3 and called defensins. The mixture killed Staphylococcus aureus, Pseudomonas and E. coli in the right conditions and also killed the fungus Cryptococcus. HNP-1 is the prototype of the human alpha-defensins.

How it kills turned out to be more specific than first thought. Defensins were assumed to punch holes in microbial membranes, but a 2010 study found that HNP-1's membrane activity did not track its killing and that it binds lipid II, a precursor of the bacterial cell wall, the same target some antibiotics use.

In people, HNP-1 is mostly measured, usually as HNP1-3 together because the assays cannot separate them. Levels rose stepwise with the severity of decompensated cirrhosis and predicted 30- and 90-day mortality better than the neutrophil-to-lymphocyte ratio; they were higher after heart attacks than in controls; and in feverish children they were higher with bacterial infections, but not useful enough to diagnose them.

HNP-1 has never been given to people as a treatment and has no human dose. Its importance is as part of how neutrophils fight infection and, potentially, as a marker of illness severity.

Structured data

At a Glance

Every value in this table is printed from the Grey Peptides dataset, the same record the compound explorer and comparison tool read, so the three can never disagree.

ClassA 30-amino-acid cationic antimicrobial α-defensin — the prototype human neutrophil peptide — stored in the azurophilic granules of neutrophils and released into the phagosome and, during degranulation, into the extracellular environment.
SequenceACYCRIPACIAGERRYGTCIYQGRLWAFCC (disulfides Cys2-Cys30, Cys4-Cys19, Cys9-Cys29)
FormulaC150H222N44O38S6
Molecular weight3442.06 g/mol
Half-lifenot applicable — endogenous granule-stored peptide
US statusResearch Chemical
Evidence levelLow
Last reviewed2026-10-05
Evidence

Published Research

These studies were read from their PubMed abstracts on October 5, 2026.

In Vitro1985

Discovery: defensins from human neutrophils

Granule extracts of normal human neutrophils contained three antibiotic peptides under 3.5 kDa, named HNP-1, -2 and -3; the mixture killed S. aureus, P. aeruginosa and E. coli in nutrient-containing buffer and Cryptococcus neoformans in nutrient-free buffer.

PMID: 2997278
In Vitro2010

It binds the cell-wall precursor lipid II

Membrane activity of human alpha-defensins did not correlate with bacterial killing; HNP-1 bound lipid II, the bacterial cell-wall precursor, pointing to a more specific mechanism than membrane disruption.

PMID: 20214904
Human2023

A mortality marker in cirrhosis

Plasma HNP1-3 rose stepwise from compensated cirrhosis to acute-on-chronic liver failure grade 3 and independently predicted 30- and 90-day mortality, with areas under the curve of 0.85 and 0.89.

PMID: 36648384
Human2021

After heart attacks

HNP1-3 was higher in patients with acute myocardial infarction than in controls (6.5 against 2.8 ng/mL), but did not differ significantly with the severity of coronary disease.

PMID: 33709917
Human2023

Fever in children: not a good test

Among 111 children, HNP1-3 was higher with bacterial infections, but its diagnostic value was low; CRP and neutrophil count did better, and the authors did not recommend it for routine use.

PMID: 37892652
Safety

Side Effects & Contraindications

Reported Side Effects

Not applicable.

● HNP-1 has never been given to people as a treatment
● Any product sold as HNP-1 is untested for human use

Contraindications & Cautions

Not a medicine, so there is no label and no formal contraindication.

● No approved product exists; nothing sold as this peptide has been tested in people as a treatment
● Research-grade material has no quality control for human use
Questions

Frequently Asked Questions

?What is HNP-1?

An alpha-defensin stored in neutrophils, discovered in 1985, that helps kill bacteria and fungi.

?Is HNP-1 used as a blood test?

Not routinely. Levels rise with severe illness and predicted mortality in cirrhosis, but in feverish children it was not a useful test.

?Is HNP-1 a treatment?

No. It has never been developed or given as a medicine.

Bibliography

References

  1. [pubmed] Ganz T, et al. "Defensins. Natural peptide antibiotics of human neutrophils." J Clin Invest, 1985;76(4):1427-35. PMID: 2997278.
  2. [pubmed] de Leeuw E, et al. "Functional interaction of human neutrophil peptide-1 with the cell wall precursor lipid II." FEBS Lett, 2010;584(8):1543-8. PMID: 20214904.
  3. [pubmed] Huang C, et al. "Plasma human neutrophil peptides as biomarkers of disease severity and mortality in patients with decompensated cirrhosis." Liver Int, 2023;43(5):1096-1106. PMID: 36648384.
  4. [pubmed] Katkat F, et al. "Human neutrophil peptides 1-3 level in patients with acute myocardial infarction and its relation with coronary artery disease severity." Turk Kardiyol Dern Ars, 2021;49(2):120-126. PMID: 33709917.
  5. [pubmed] Kassem E, et al. "The Diagnostic Value of Human Neutrophilic Peptides 1-3 in Acute Pediatric Febrile Illness." J Clin Med, 2023;12(20). PMID: 37892652.
  6. [pubmed] Lehrer RI, et al. "α-Defensins in human innate immunity." Immunol Rev, 2012;245(1):84-112. PMID: 22168415.

Sources & Citations

Studies from their PubMed abstracts, read October 5, 2026.

Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Consult a licensed healthcare provider before making health decisions.

Last reviewed: 2026-10-05