What Is LL-37?
LL-37 (Cathelicidin) is classified as a antimicrobial peptide peptide. The only human cathelicidin antimicrobial peptide. LL-37 is a 37-amino acid cationic peptide that directly disrupts microbial membranes (bacteria, viruses, fungi) and neutralizes bacterial endotoxins (LPS). Beyond direct antimicrobial action, LL-37 modulates innate immunity by chemoattracting neutrophils, monocytes, and T-cells to infection sites. Promotes wound healing via EGFR-mediated keratinocyte migration and angiogenesis. Demonstrates potent anti-biofilm properties against resistant organisms.
It is extensively evaluated in laboratory and clinical settings for its potential to drive broad-spectrum antimicrobial, anti-biofilm, wound healing, immune modulation, anti-inflammatory. Researchers target LL-37 for its ability to interact with specific cellular and molecular pathways, making it a compound of significant interest across multiple therapeutic domains.
Endogenous human peptide with well-characterized biology. Cytotoxic to eukaryotic cells at high concentrations (>25mcg/mL). Concentration-dependent effects: low doses immunomodulatory, high doses cytotoxic. Growing research interest in CIRS/mold illness protocols. Not FDA-approved as a therapeutic.
How Does LL-37 Work?
The only human cathelicidin antimicrobial peptide. LL-37 is a 37-amino acid cationic peptide that directly disrupts microbial membranes (bacteria, viruses, fungi) and neutralizes bacterial endotoxins (LPS). Beyond direct antimicrobial action, LL-37 modulates innate immunity by chemoattracting neutrophils, monocytes, and T-cells to infection sites. Promotes wound healing via EGFR-mediated keratinocyte migration and angiogenesis. Demonstrates potent anti-biofilm properties against resistant organisms.
At the molecular level, LL-37 operates through pathways characteristic of the Antimicrobial Peptide class. By interacting with target receptors and downstream signaling cascades, the compound initiates biological responses associated with broad-spectrum antimicrobial, anti-biofilm, wound healing, immune modulation, anti-inflammatory.
Expected Research Timeline
Weeks 2–4
Reduced infection symptoms; improved wound healing at treatment sites; systemic immune upregulation
Months 2–3
Sustained antimicrobial effects; biofilm disruption in chronic infections; improved mucosal barrier integrity
Long-Term
Best used in targeted protocols for active infections or chronic immune challenges; not typically used indefinitely
What Does the Research Say?
The following are key findings from peer-reviewed studies on LL-37, indexed on PubMed and equivalent databases:
[1]LL-37 broad-spectrum antimicrobial and immunomodulatory effects
Comprehensive review of LL-37's dual antimicrobial and immunomodulatory functions, including membrane disruption, chemotaxis, cytokine regulation, and wound healing promotion.
Evidence: moderate[2]LL-37 anti-biofilm activity against resistant pathogens
Overhage et al.: LL-37 inhibits biofilm formation by Pseudomonas aeruginosa at sub-MIC concentrations, affecting bacterial attachment, migration, and quorum sensing.
Evidence: preclinical[3]LL-37 promotes wound healing via EGFR transactivation
Tokumaru et al.: LL-37 promotes wound re-epithelialization by stimulating keratinocyte migration through EGFR transactivation, providing mechanistic basis for wound-healing applications.
Evidence: preclinical[4]Cathelicidin deficiency increases susceptibility to infection
Chromek et al.: Studies in CAMP-knockout models demonstrate that cathelicidin deficiency significantly increases susceptibility to urinary tract and skin infections, validating LL-37's critical role in host defense.
Evidence: preclinical[5]LL-37 in chronic inflammatory conditions and immune regulation
Kahlenberg et al.: Review of LL-37's role in autoimmune and chronic inflammatory conditions including psoriasis, lupus, and rosacea. LL-37 acts as a danger signal activating dendritic cells and driving type I interferon production.
Evidence: moderateSafety & Side Effects
Endogenous human peptide with well-characterized biology. Cytotoxic to eukaryotic cells at high concentrations (>25mcg/mL). Concentration-dependent effects: low doses immunomodulatory, high doses cytotoxic. Growing research interest in CIRS/mold illness protocols. Not FDA-approved as a therapeutic.
| Side Effect | Incidence | Severity |
|---|---|---|
| Injection site reaction (redness, swelling) | ~15% of users | mild |
| Flu-like symptoms (immune activation) | ~10% of users | mild |
| Mild fever | ~5% of users | mild |
| Fatigue | ~8% of users | mild |
FDA Status: Not Approved for Human Therapeutic Use
LL-37 is not currently FDA-approved for human use. It is available for research purposes only. Always consult a licensed healthcare provider.
How Is LL-37 Used?
Route
SubQ
Dose Range
100–100 mcg
Frequency
7x/wk
Cycle
6–6 wk
Timing: Any time
Notes: Research doses typically 50-200mcg SubQ. Start low (50mcg) to assess tolerance. Also used topically for wound applications. Practitioners in CIRS protocols often use nebulized delivery for respiratory infections.
All dosing information reflects parameters reported in published research literature and is not intended as clinical guidance. Usage of any peptide should be supervised by a qualified healthcare professional.
LL-37 vs. Related Compounds
| Compound | Primary Use |
|---|---|
| LL-37(this page) | Broad-spectrum antimicrobial, anti-biofilm, wound healing, immune modulation, anti-inflammatory |
| BPC-157 | Injury recovery, gut healing, tissue repair, reduced inflammation |
| KPV | Gut/injury healing, inflammation reduction |
| Thymosin Alpha-1 | Immune support, antiviral, recovery |
Where to Source LL-37 for Research
Purchasing ultra-high purity, laboratory-grade peptides is critical for verifiable research. We only recommend vendors providing independent, third-party HPLC Certificates of Analysis (COA).
Disclosure: PeptiDex may earn a commission from purchases. This does not affect our recommendations. We exclusively feature vendors that pass our strict quality verification protocols.
Frequently Asked Questions
What is LL-37?
LL-37 is a antimicrobial peptide peptide. The only human cathelicidin antimicrobial peptide. LL-37 is a 37-amino acid cationic peptide that directly disrupts microbial membranes (bacteria, viruses, fungi) and neutralizes bacterial endotoxins (LPS). Beyond direct antimicrobial action, LL-37 modulates innate immunity by chemoattracting neutrophils, monocytes, and T-cells to infection sites. Promotes wound healing via EGFR-mediated keratinocyte migration and angiogenesis. Demonstrates potent anti-biofilm properties against resistant organisms.
What are the primary research benefits of LL-37?
Published research identifies primary mechanisms targeting: Broad-spectrum antimicrobial, anti-biofilm, wound healing, immune modulation, anti-inflammatory. These findings come from 5+ peer-reviewed studies indexed in our database.
What is the half-life of LL-37?
In published pharmacokinetic data, LL-37 demonstrates a half-life of approximately 4 hours.
Is LL-37 FDA approved?
LL-37 is not currently FDA-approved for human therapeutic use. It is classified as a research compound and is studied under investigational protocols. Always consult a healthcare provider.
What are common side effects of LL-37?
Reported side effects in published literature include Injection site reaction (redness, swelling) (~15% of users), Flu-like symptoms (immune activation) (~10% of users), Mild fever (~5% of users), Fatigue (~8% of users). Most are classified as mild in severity.
How is LL-37 administered?
In research settings, LL-37 is typically administered via SubQ. Research doses typically 50-200mcg SubQ. Start low (50mcg) to assess tolerance. Also used topically for wound applications. Practitioners in CIRS protocols often use nebulized delivery for respiratory infections.
Sources
- LL-37 broad-spectrum antimicrobial and immunomodulatory effects. View on PubMed
- LL-37 anti-biofilm activity against resistant pathogens. View on PubMed
- LL-37 promotes wound healing via EGFR transactivation. View on PubMed
- Cathelicidin deficiency increases susceptibility to infection. View on PubMed
- LL-37 in chronic inflammatory conditions and immune regulation. View on PubMed