Skip to content
preclinicalImmune & Inflammation

Cathelicidin

Also known as: hCAP-18, hCAP18, CAMP, Cathelicidin Antimicrobial Peptide, LL-37 Precursor

Cathelicidin (hCAP-18) is an 18 kDa precursor protein that is cleaved by proteinase 3 to release the active antimicrobial peptide LL-37 from its C-terminus. Stored in neutrophil specific granules, keratinocytes, and epithelial cells, it is the sole member of the cathelicidin family in humans. Its expression is regulated by vitamin D, making it a critical link between vitamin D status and innate immune function.

3 cited references·5 researched benefits

Quick Answer

Cathelicidin (hCAP-18) is the precursor protein of LL-37, the only human cathelicidin antimicrobial peptide. Stored in neutrophils and epithelial cells, it is cleaved by proteinase 3 to release the active LL-37 fragment during infection. Cathelicidin expression is directly regulated by vitamin D through a vitamin D response element in its gene promoter, linking vitamin D status to antimicrobial defense. Research focuses on boosting cathelicidin expression as an immune enhancement strategy.

Key Facts

Mechanism
hCAP-18 is synthesized as an inactive precursor containing a conserved cathelin-like domain and a C-terminal antimicrobial domain. Upon neutrophil degranulation or keratinocyte activation, proteinase 3 cleaves the holoprotein between Ala103 and Leu104, releasing the 37-amino acid LL-37 peptide. The cathelin pro-domain itself has anti-protease and immunomodulatory activities. The CAMP gene encoding cathelicidin contains a vitamin D response element (VDRE) in its promoter, making expression directly dependent on circulating 1,25-dihydroxyvitamin D3 levels. This vitamin D-cathelicidin-LL-37 axis is a central mechanism in innate antimicrobial defense.
Research Status
preclinical
Half-Life
Precursor (hCAP-18): hours in granule storage; cleaved LL-37: ~15 minutes in serum
Molecular Formula
C₇₉₂H₁₂₇₀N₂₂₂O₂₃₈S₅
Primary Use
Immune & Inflammation
Table of Contents

Benefits

  • Primary source of LL-37, the body's key broad-spectrum antimicrobial peptidestrong
  • Expression boosted by vitamin D supplementation, providing a drugless immune enhancement strategystrong
  • Cathelin pro-domain has independent anti-protease and anti-inflammatory activitymoderate
  • Biomarker for innate immune competence and vitamin D functional statusmoderate
  • Target for therapeutic upregulation in immunocompromised patients and chronic infectionspreliminary

Dosage Protocols

RouteDosage RangeFrequencyNotes
Indirect (vitamin D supplementation)2,000–5,000 IU vitamin D₃ dailyDailyOptimizing vitamin D levels to 50-80 ng/mL increases endogenous cathelicidin/LL-37 expression
Research use onlyVariableVariableRecombinant hCAP-18 used in laboratory studies; no direct human therapeutic dosing established

Medical disclaimer

Dosage information is provided for educational reference only. Always follow your prescriber's instructions and consult a qualified healthcare provider before starting any peptide protocol.

Side Effects

  • Not administered exogenously; side effects relate to LL-37 release (see LL-37 profile)common
  • Overexpression linked to psoriasis and rosacea pathologyserious
  • Excessive cathelicidin processing may contribute to skin inflammationrare

Frequently Asked Questions

What is the difference between cathelicidin and LL-37?
Cathelicidin (hCAP-18) is the full-length precursor protein, while LL-37 is the active antimicrobial peptide fragment cleaved from its C-terminus. Think of cathelicidin as the loaded weapon and LL-37 as the bullet. The precursor is stored safely in neutrophil granules and is only processed into active LL-37 when needed during infection or inflammation. LL-37 has a separate profile on this site with detailed dosing and clinical information.
Does vitamin D really boost cathelicidin levels?
Yes. The cathelicidin gene (CAMP) has a vitamin D response element in its promoter, making its expression directly dependent on vitamin D levels. Multiple studies have demonstrated that vitamin D supplementation increases cathelicidin expression in monocytes, neutrophils, and epithelial cells. This is believed to be a major reason why vitamin D deficiency increases susceptibility to infections, particularly tuberculosis and respiratory infections.
Why is cathelicidin important for immune defense?
Cathelicidin is the sole human source of LL-37, which is the only cathelicidin antimicrobial peptide in the human genome. This makes it an irreplaceable component of innate immunity. Individuals with reduced cathelicidin expression (due to vitamin D deficiency, genetic variants, or immunosuppression) are more susceptible to bacterial infections, particularly tuberculosis, urinary tract infections, and skin infections.

References

  1. 1
    Cutting edge: 1,25-dihydroxyvitamin D3 is a direct inducer of antimicrobial peptide gene expression(2004)PubMed ↗
  2. 2
    Cathelicidins: a family of endogenous antimicrobial peptides(2006)PubMed ↗
  3. 3
    Toll-like receptor triggering of a vitamin D-mediated human antimicrobial response(2006)PubMed ↗

Latest Research

Last updated: 2026-02-19