Research Only Immune & Anti-Inflammatory

hBD-2

also known as: human β-defensin 2, DEFB4A, DEFB4, defensin β2, hBD2, SAP1 — skin-antimicrobial peptide 1

The inducible β-defensin — cloned by Harder, Bartels, Christophers and Schröder (Nature 1997) from the lesional scales of psoriasis patients, with the paper framing psoriatic skin as a paradoxical "almost-never-infected" phenotype driven by massive β-defensin induction. Induced by TLR / NF-κB signalling in response to bacterial lipopolysaccharide and pro-inflammatory cytokines (IL-1, TNF-α).

A 41-amino-acid cationic β-defensin originally purified from the scale extracts of psoriasis patients (Harder, Bartels, Christophers, Schröder; Nature, 1997) and named SAP1 before its defensin assignment was recognised. Unlike hBD-1, hBD-2 expression is strongly inducible by TLR-mediated NF-κB signalling — bacterial LPS, lipoteichoic acid, flagellin and pro-inflammatory cytokines (IL-1β, TNF-α, IL-17) all markedly upregulate DEFB4A transcription in keratinocytes, bronchial epithelium, intestinal epithelium and other barrier epithelia. Expression in psoriatic skin is 100-fold or more above normal, contributing to the low clinical infection rate of psoriatic lesions.

Mechanism of action

Classical β-defensin mechanism: cationic membrane permeabilisation of bacterial, fungal and enveloped-viral targets. In-vitro spectrum is broadest against Gram-negative bacteria (E. coli, P. aeruginosa, K. pneumoniae) and C. albicans, with weaker Gram-positive activity. Beyond direct microbicidal activity, hBD-2 is a potent chemokine for CCR6-expressing immature dendritic cells and memory T cells (Yang, Chertov, Bykovskaia, Chen, Buffo, Shogan, Anderson, Schröder, Wang, Howard, Oppenheim; Science 1999) — effectively recruiting adaptive immunity to the site of innate alarm. Also signals through EGFR transactivation in keratinocytes to stimulate wound-edge migration. Induction is NF-κB- and AP-1-dependent; IL-17/IL-22 from Th17 cells are particularly potent inducers in skin and mucosa.

Primary uses

  • Research reagent for antimicrobial peptide and epithelial-immunity studies
  • Inflammatory skin disease research (psoriasis, atopic dermatitis — where hBD-2 induction is paradoxically reduced)
  • Investigational recombinant therapy for ulcerative colitis and mucositis (Phase 2)
  • Clinical biomarker research (salivary and sputum hBD-2 in infection and inflammation)

Typical dosing

Not established

⚠ No human dosing established for approved use. Investigational recombinant hBD-2 (Defensin Therapeutics) has been administered orally in early-phase ulcerative colitis trials; specific dose ranges are trial-specific and not yet in general clinical use.

Regulatory status

Not a drug, though recombinant hBD-2 has been evaluated as an investigational agent for inflammatory bowel disease and oral mucositis in early-phase work (Defensin Therapeutics / Novozymes recombinant hBD-2; Phase 2 trial in distal ulcerative colitis reported 2023). No regulatory approval as of 2026.

References

  1. [pubmed] Harder J, Bartels J, Christophers E, Schröder JM. "A peptide antibiotic from human skin." Nature, 1997;387(6636):861. (First isolation of hBD-2.)
  2. [pubmed] Yang D, Chertov O, Bykovskaia SN, et al. "Beta-defensins: linking innate and adaptive immunity through dendritic and T cell CCR6." Science, 1999;286(5439):525-528.
  3. [review] Pazgier M, Hoover DM, Yang D, Lu W, Lubkowski J. "Human beta-defensins." Cell Mol Life Sci, 2006;63(11):1294-1313.

Related peptides

hBD-1

The constitutive epithelial β-defensin — first isolated from haemodialysate urine by Bensch, Schröder and colleagues (FEBS Letters 1995). Constitutively expressed (unlike hBD-2 and hBD-3, which are inducible), salt-sensitive in standard assays, and a major component of urogenital and airway surface antimicrobial defense.

hBD-3

The broad-spectrum β-defensin — active against Gram-positive, Gram-negative and fungal targets, and largely salt-insensitive (unlike hBD-1). Isolated independently in 2001 by Harder et al. and by García et al. from psoriatic skin and tonsil respectively. The β-defensin most studied for clinical translation because of its salt tolerance.

HNP-1

The prototype human α-defensin — isolated from neutrophil granules by Ganz, Selsted and Lehrer in 1985; the dominant antimicrobial peptide in human neutrophils and a workhorse molecule of innate immunity. Research peptide only: no defensin has ever been developed as an approved drug.

HD5

The Paneth cell α-defensin — the dominant antimicrobial peptide of the human small intestine, stored at millimolar concentrations in Paneth cell secretory granules and released into the crypt lumen upon cholinergic or bacterial stimulus. Reduced HD5 expression is a recognised feature of ileal Crohn disease.

HD6

The Paneth cell α-defensin that does not kill directly — HD6 traps enteric pathogens by self-assembling into fibrillar "nanonets" (Chu et al., Science 2012), a mechanism unique among the defensin family. Poor microbicidal activity in vitro was a decade-long puzzle until the trapping mechanism was discovered.
Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.