The human cathelicidin antimicrobial peptide — endogenous first-line defense that’s become an off-label tool for chronic infections, biofilm disruption, and immune protocols.
LL-37 is the only cathelicidin antimicrobial peptide in humans — a 37 amino acid peptide (hence the name) produced by skin, respiratory, and immune cells as part of innate immune defense. It kills a wide range of bacteria, viruses, and fungi by disrupting their membranes, and also modulates the host inflammatory response.
LL-37 is endogenous and levels decline with age, chronic infection, or vitamin D deficiency (vitamin D directly upregulates cathelicidin production). Synthetic LL-37 is used off-label in chronic infection protocols (Lyme, chronic sinusitis, biofilm-related conditions) and immune-support contexts.
Not FDA approved. Not WADA prohibited. Research chemical with moderate scientific interest for antimicrobial and immunomodulatory applications.
LL-37’s amphipathic helical structure inserts into microbial membranes (which have different lipid composition than host cells) and disrupts them. Broad-spectrum against gram-positive, gram-negative, fungi, and some enveloped viruses.
Shown to inhibit and disrupt biofilms of Pseudomonas, Staphylococcus, and others. Biofilms are why some chronic infections are so hard to treat with conventional antibiotics; LL-37 is one of the few tools that works against them.
At sub-lethal concentrations, LL-37 modulates immune cell behavior — chemotaxis, dendritic cell differentiation, cytokine release. Dual action (direct antimicrobial + immune tuning) is why it outperforms pure antibiotics in some contexts.
Vitamin D is a direct upregulator of endogenous LL-37 production. Adequate vitamin D status supports cathelicidin synthesis; LL-37 supplementation can be viewed as working on the same axis.
| Benefit | Evidence |
|---|---|
| Broad antimicrobial | In-vitro activity against extensive pathogen list; in-vivo results less uniform |
| Biofilm disruption | Consistent preclinical; used in chronic sinusitis and biofilm-related Lyme protocols |
| Wound healing | Accelerates closure and reduces infection in chronic wounds |
| Immune modulation | Reduces LPS-driven inflammation while preserving pathogen clearance |
| Chronic Lyme adjunct | Anecdotal; used alongside Thymosin Alpha-1 and LDN in complex chronic infection protocols |
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Start Tracking FreeIn chronic infection / biotoxin illness protocols, LL-37 is often combined with Thymosin Alpha-1 (immune restoration), VIP (after Shoemaker Step 11), and Low Dose Naltrexone. Adequate vitamin D (target 40–60 ng/mL) supports the protocol since it drives endogenous cathelicidin.
LL-37 can trigger strong Herxheimer-like reactions in biofilm-loaded patients. Start at 100 mcg / 3×/week for the first 2 weeks, titrate up as tolerated.
5 mg vial + 2 mL BAC water = 2500 mcg/mL
| Dose | Volume | Syringe Units |
|---|---|---|
| 100 mcg | 0.04 mL | 4 units |
| 250 mcg | 0.10 mL | 10 units |
| 500 mcg | 0.20 mL | 20 units |
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LL-37 is not only antimicrobial — published work (PMIDs 35387840, 40869425) documents cytotoxicity to host endothelial cells (particularly under dysfunctional autophagy) and links LL-37 to endothelial dysfunction, atherogenic signaling, and impaired autophagy at higher concentrations. In psoriasis it acts as a TLR7/TLR9 autoantigen that drives plasmacytoid dendritic cell activation (PMIDs 32582207, 40869425) — a mechanism that may extend to other TLR-driven autoimmune dermatological conditions, not just psoriasis. PMID 40869425 also identifies low proteolytic stability as a known clinical limitation, which affects how predictably in-vivo peptide activity tracks the injected dose. Use caution if you have cardiovascular disease, atherosclerosis, or known endothelial dysfunction, and avoid higher-end doses without a clear reason to escalate.
LL-37 (Cathelicidin) is a research peptide not approved by the FDA for human use. It is sold only as a research chemical, and StackTrax does not endorse or facilitate personal use.
Quality varies enormously among research-chemical suppliers. At minimum, look for:
StackTrax’s preferred partner NextGen Peptides does not currently carry LL-37 (Cathelicidin)in their catalog, which is why you don’t see a direct purchase link here. Other major research-chemical suppliers carry it; we don’t specifically recommend one for this compound.
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeDisclaimer: This guide is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. The compounds discussed are not FDA approved for human use. Always consult a qualified healthcare provider before starting any new supplement or peptide protocol. StackTrax does not sell peptides or supplements directly — purchase links go to third-party vendors. StackTrax is not responsible for the products, quality, or business practices of any third-party vendor. This page contains affiliate links — StackTrax may earn a commission on purchases at no extra cost to you.
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StackTrax guides cover peptides and compounds that are not FDA-approved for the uses discussed. The dosing, reconstitution, and safety information is compiled from published research and community protocols for educational purposes only.
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