HNP3

HNP-3, or human neutrophil peptide 3, is a small antimicrobial peptide that belongs to the alpha-defensin family. It is produced mainly by neutrophil granulocytes and stored in their azurophilic granules. During an immune response, neutrophils release HNP-3 by degranulation, contributing to the innate defense against invading microbes.

The HNP-3 peptide is encoded by the DEFA3 gene, located in a defensin gene cluster on chromosome 8. This cluster also contains other alpha-defensin genes such as DEFA1 and DEFA4. The genes in this region can vary in copy number between individuals, a phenomenon known as copy number variation, which has been studied for potential links to susceptibility to inflammatory and infectious diseases.

Biochemically, HNP-3 is a cysteine-rich peptide of about 29 to 34 amino acids. Its cationic, disulfide-stabilized structure is typical of defensins and underpins its ability to interact with and disrupt microbial membranes. In addition to direct antimicrobial activity, defensins, including HNP-3, are thought to influence immune system processes to some extent, potentially affecting inflammatory signaling and cell recruitment in certain contexts.

Clinical and research relevance of HNP-3 lies in its role as part of the neutrophil antimicrobial arsenal. Variation in defensin gene copy number and expression has been examined in relation to inflammatory and infectious diseases, with mixed findings. HNP-3 levels and activity may be elevated at sites of infection or inflammation as part of neutrophil responses.