hCAP-18 cleavage
Enzymes release the active LL-37 fragment from its human precursor protein.
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Innate Immunity Peptide
LL-37
Cathelicidin • Innate Immunity • Antimicrobial Research
LL-37 is the human cathelicidin antimicrobial peptide. It participates in innate immune defense, microbial-membrane disruption, inflammatory signaling, and wound repair. Topical wound research exists, but injectable LL-37 has no established human safety or efficacy profile.
At a glance
LL-37 Quick Reference
- Community range
- Members onlySign in to view dosing details.
- Cycle
- Members onlySign in to view dosing details.
- Research class
- CathelicidinHuman antimicrobial and innate immune peptide
- Evidence
- Topical wound studiesInjectable outcomes remain unstudied in people
Overview
What Is LL-37?
LL-37 is the 37-amino-acid antimicrobial fragment cleaved from the precursor protein hCAP-18. It is the only human cathelicidin. Its name comes from the two leucines at its start and its 37-residue length.
Immune and epithelial cells produce LL-37 at surfaces including skin, lungs, and the gastrointestinal tract. It can disturb microbial membranes, bind bacterial toxins, influence immune-cell signaling, and participate in wound repair. Those overlapping actions have drawn interest in antimicrobial resistance and biofilm research.
Evidence depends on the setting. Laboratory work establishes antimicrobial activity, while controlled human studies have examined topical LL-37 for chronic wounds. Neither source validates a SubQ dose or demonstrates that injecting it treats persistent infection or immune dysfunction.
Mechanism
LL-37 Mechanism of Action
Microbial membranes
LL-37 can interact with and disrupt microbial membranes in laboratory models.
Biofilm and toxin effects
Research examines biofilm disruption and binding of bacterial lipopolysaccharide.
Immune and repair signaling
It affects inflammatory pathways, cell recruitment, and wound-healing responses; excessive activity may be harmful.
Research findings
LL-37 Benefits
Most benefits below are laboratory or topical-wound findings; none establishes injectable treatment of infection.
Antimicrobial Activity
Laboratory work shows activity against bacterial, fungal, and some viral models.
Biofilm Research
LL-37 can disturb biofilm structures in vitro, potentially increasing microbial exposure to immune defenses.
Topical Wound Healing
Controlled topical studies have evaluated wound closure and re-epithelialization; this is a different route from SubQ.
Immune Modulation
It influences immune-cell recruitment and inflammatory signaling in ways that vary by context.
Antibiotic Synergy
In-vitro studies have explored interactions with conventional antibiotics; clinical combination benefit is unproven.
Endotoxin Binding
Laboratory research shows binding of bacterial lipopolysaccharide and related inflammatory pathways.
Protocol planning
LL-37 Dosing Protocol
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Preparation
LL-37 Reconstitution
Reconstitution Example
5mg vial + 2mL bacteriostatic water
Result2.5mg/mL
Reconstitution steps
1
Prepare
Wash your hands, clean the work surface, and wipe both vial stoppers with alcohol. Allow them to dry.
2
Add diluent slowly
Use a new sterile syringe and needle to direct the selected volume of compatible diluent down the inside wall of the vial.
3
Dissolve gently
Swirl or roll the vial until the contents dissolve; do not shake.
4
Storage
Store refrigerated at 2–8°C (36–46°F) and protected from light when the product instructions support this. Record the reconstitution date in your research journal.
N=1 reports
LL-37 Community Experience
Self-reported anecdotal experiences aggregated from public & private peptide community discussions and anonymous peptideprotocols.app user reports. This information does not carry the same weight as published research.
Positive Reports
- Some users describe improved recovery from persistent skin or immune-related problems.
- Interest in biofilm and gut research drives many community accounts.
- Short, targeted use is preferred by some over continuous use.
Negative & Mixed Reports
- Injection-site burning, redness, swelling, or itching are common complaints.
- Early fatigue, body aches, low fever, or malaise are sometimes described.
- Some report no clear benefit; inflammatory symptoms can be hard to interpret.
Stacking & synergy
LL-37 Stacking & Synergy
LL-37 has broad immune activity. These pairings are research discussions, not established combination protocols.
LL-37 + BPC-157
The proposed pairing joins antimicrobial and tissue-repair interests; controlled combination outcomes are unavailable.
LL-37 + Thymosin Alpha-1
Thymosin Alpha-1 centers on adaptive immune signaling, while LL-37 participates in innate defense. Complementarity is theoretical.
LL-37 + Antibiotics
Laboratory synergy with some antibiotics does not justify changing prescribed treatment; any combination needs clinical coordination.
Safety notes
LL-37 Side Effects & Safety
Topical trial tolerability cannot establish the safety of injectable LL-37. Its effects can vary by concentration and inflammatory setting.
LL-37 can amplify inflammatory pathways in some settings. New fever, worsening inflammation, or a severe injection reaction warrants medical assessment.
Reported Effects
- Injection-site redness, swelling, burning, stinging, or itching.
- Flu-like symptoms including fatigue, aches, low fever, or malaise.
Potential Concerns
- Possible worsening of psoriasis, rosacea, lupus, or other inflammatory conditions.
- Host-cell toxicity at high concentrations in laboratory research.
- Unknown long-term effects and product-quality risks for injections.
LL-37 Precautions
Avoid or Discuss With a Clinician If
- Active autoimmune or inflammatory disease, especially psoriasis, lupus, or rosacea.
- Known hypersensitivity to LL-37 or a formulation ingredient.
- Pregnancy or breastfeeding; human safety data are unavailable.
Use Caution With
- A history of autoimmune disease or inflammatory bowel symptoms.
- Immunosuppressive therapy or concurrent treatment for an active infection.
- An unverified injectable product or uncertain sterility.
LL-37 is not FDA approved for injectable human use; topical research does not validate SubQ use.
Final verdict
Peptide Protocols Verdict on LL-37
Not medical advice. This editorial is our own opinion piece based off the experience of our own lab rats.
Our opinionated opinion
We see LL-37 as a powerful antimicrobial research peptide. People around us have shared encouraging stories about persistent issues, but we have not run it ourselves. That matters: their experiences are useful context, not proof that an injection clears an infection or resets immunity.
We would treat LL-37 as a specialized, short-purpose research tool rather than something for casual daily use. Its inflammatory potential gives us pause, especially for anyone with autoimmune or skin-inflammatory problems. The topical wound signal is interesting, but the missing injectable safety data keeps our grade at C.