LL-37
LL-37 (Cathelicidin)
LL-37 is the only known member of the cathelicidin family of antimicrobial peptides in humans, consisting of 37 amino acids and naturally produced by neutrophils, epithelial cells, and keratinocytes as part of innate immunity. It is primarily researched for its potent antimicrobial, immunomodulatory, and wound-healing properties, with experimental use in treating chronic wounds, skin infections, and inflammatory conditions. Beyond its antimicrobial role, LL-37 has attracted interest for its ability to modulate inflammation, promote angiogenesis, and potentially support cancer immunosurveillance.
Mechanism of Action
LL-37 exerts antimicrobial effects by disrupting bacterial, fungal, and viral membranes through electrostatic interactions with negatively charged phospholipids, leading to membrane permeabilization and microbial cell death. It also acts as an immunomodulatory agent by binding to pattern recognition receptors, activating TLR4 signaling pathways, promoting chemokine release, and recruiting immune cells including neutrophils and monocytes to sites of infection. Additionally, LL-37 stimulates wound healing through EGFR transactivation, VEGF upregulation, and promotion of keratinocyte migration and proliferation.
Evidence by Health Goal(18 goals)
Dosing Protocols
Morning, subcutaneous injection into abdominal or thigh tissue
Cycle: 4-8 weeks on, 4 weeks off
Subcutaneous administration is the most common research protocol. No established human clinical dosing exists; these ranges are extrapolated from preclinical studies and anecdotal research use. Reconstitute with bacteriostatic water and store refrigerated.
Applied directly to wound, lesion, or target skin area; cover with dressing if treating open wounds
Topical application is the most clinically studied route for wound healing and skin infections. Compounded creams or gels are typically used. Most appropriate for localized antimicrobial or wound-healing applications.
As needed for upper respiratory or sinonasal infection management
Cycle: 2-4 weeks maximum continuous use
Nasal administration is investigational for sinonasal conditions such as chronic rhinosinusitis. Delivered via saline-based nasal spray or irrigation. Limited clinical data available; consult a physician before use.
Safety & Side Effects
LL-37 has a relatively limited human clinical safety dataset, with most evidence derived from in vitro, animal, and small Phase I/II trials; it is not FDA-approved for therapeutic use and is available only as a research peptide in most jurisdictions. Its immunomodulatory potency warrants caution in individuals with autoimmune diseases, active malignancies, or those on immunosuppressive therapy, as it may unpredictably shift immune responses.
Possible Side Effects
- !Injection site reactions including redness, swelling, and localized pain
- !Transient burning or stinging sensation upon topical or nasal application
- !Pro-inflammatory flares in individuals with autoimmune conditions due to immune activation
- !Nausea or mild systemic discomfort with higher systemic doses
- !Potential exacerbation of inflammatory skin conditions such as psoriasis or rosacea with topical use
- !Theoretical risk of dysregulated immune activation with chronic systemic use
- !Hypersensitivity or allergic reaction in sensitized individuals
Interactions
- -May counteract or interfere with immunosuppressive drugs (e.g., corticosteroids, cyclosporine) by promoting immune activation
- -Potential additive pro-inflammatory effects when combined with other immunostimulatory peptides such as thymosin alpha-1 or LL-37 analogs
- -May enhance activity of topical antibiotics by disrupting bacterial membranes and improving antibiotic penetration
- -Use caution with anticoagulants; LL-37 promotes angiogenesis and may modestly influence platelet aggregation and coagulation pathways
- -Could theoretically exacerbate autoimmune conditions (e.g., lupus, psoriasis) by amplifying innate immune signaling
Cost & Where to Buy
Research-grade LL-37 peptide is available from peptide vendors at approximately $30-$120 per vial (1-5mg); monthly cost depends on dose, route, and frequency. Topical compounded formulations from compounding pharmacies may cost $60-$200 per preparation. Purity and source significantly affect pricing and safety.
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