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Immune

LL-37 Guide & Tableau de Dose

An antimicrobial host-defense peptide studied for immune modulation.

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LL-37 — Tableau de dose
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What is LL-37?

LL-37 is a small protein fragment — just 37 amino acids long — that your body makes naturally. It belongs to a family of molecules called cathelicidins, which are part of the innate immune system (the fast-acting, first-line defense your body deploys before more targeted immune responses kick in). LL-37 is the only cathelicidin found in humans, and it shows up in skin, saliva, lungs, and many other tissues.[1] Because it sits at the crossroads of fighting infections and talking to immune cells, researchers are fascinated by what it might do.

Important note: LL-37 is a research compound. It is not approved for human therapeutic use. Everything on this page describes laboratory and preclinical findings only — not medical advice.

How LL-37 Works

Think of LL-37 as a Swiss Army knife for your immune system. Its shape is amphipathic — one side of the molecule loves water, the other repels it. That split personality lets it do two very different jobs.

  • Direct attack: LL-37 can wedge itself into the outer membrane of bacteria, essentially poking holes in them until they fall apart.[3]
  • Immune messenger: LL-37 also acts like an alarm signal. It binds to receptors on immune cells — neutrophils, macrophages, and others — telling them to move toward a threat, ramp up inflammation, or sometimes calm it back down.[2]

Researchers describe LL-37 as an alarmin: a danger signal that wakes up nearby immune cells and recruits them to trouble spots.[6] Its structural flexibility means it can adapt its shape depending on its surroundings, which helps explain its remarkably broad range of activities.

What the Research Shows

Fighting Bacteria — Even in Biofilms

Biofilms are slimy communities of bacteria that stick to surfaces (like medical devices or teeth) and are notoriously hard to kill with standard antibiotics. Lab studies show LL-37 can disrupt biofilms formed by dangerous pathogens including Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli. It works by blocking bacteria from sticking, interfering with their chemical communication (called quorum sensing), and breaking down the protective matrix they hide inside.[3]

Modulating the Immune Response

LL-37 doesn't just kill microbes — it fine-tunes immune activity. Different fragments of the LL-37 molecule (such as FK-13 and IG-20) appear to interact with specific immune receptors, helping researchers understand which part of the peptide drives immunomodulation.[2] In neutrophils, LL-37 can trigger a dramatic process called NETosis — where cells release sticky webs of DNA and proteins (called NETs) that trap pathogens. This is powerful for defense, but when it goes unchecked, it can contribute to chronic inflammation.[6]

Oral Health and Tissue Regeneration

In the mouth, LL-37 helps maintain the balance between healthy bacteria and harmful ones. Disruptions in its expression have been linked to conditions like periodontitis and oral infections.[5] Beyond the mouth, studies suggest LL-37 can stimulate the migration and differentiation of mesenchymal stem cells, promote the growth of new blood vessels (angiogenesis), and support bone regeneration — all relevant to wound healing and tissue repair research.[1]

Cardiovascular Connections

More recent research has examined LL-37's role in heart-related conditions. It appears to be involved in regulating atherosclerosis (plaque buildup in arteries), thrombosis (blood clot formation), inflammatory responses in the heart, and even cardiac hypertrophy (abnormal heart enlargement). Engineered versions of LL-37 have been tested in preclinical models to explore these effects.[4]

What LL-37 Is Being Studied For

  • Antimicrobial and antibiofilm applications[3]
  • Immune modulation and inflammation regulation[2]
  • Wound healing and tissue regeneration[1]
  • Oral health and periodontal disease[5]
  • Cardiovascular disease mechanisms[4]
  • NETosis and neutrophil biology[6]

How LL-37 Is Dosed in Research

Because LL-37 is a research peptide studied across very different experimental models — cell cultures, animal studies, and early-stage investigations — there is no single standardized dosing protocol. Concentrations used in published research vary widely depending on the biological question being asked. For a structured overview of concentrations and volumes referenced in preclinical literature, see the dosage chart on this page. You can also use the calculator to work out dilutions once a target concentration has been established for a given research protocol.

Mixing and Storing LL-37

LL-37 typically arrives as a lyophilized (freeze-dried) white powder. To reconstitute it, researchers generally add sterile water or a mild acidic solution (like 0.1% acetic acid) slowly to the vial, then gently swirl — never shake vigorously, as this can damage the peptide's structure. Once dissolved, the solution should be divided into single-use aliquots to avoid repeated freeze-thaw cycles, which degrade the peptide over time. Store lyophilized peptide at -20°C, and reconstituted solution at 4°C for short-term use or -80°C for longer storage. Always let cold vials come to room temperature before opening to prevent moisture condensation from contaminating the sample.

Sources

  1. Regulation of LL-37 in Bone and Periodontium Regeneration. — Life (Basel, Switzerland), 2022. PMID 36294968.
  2. The LL-37 domain: A clue to cathelicidin immunomodulatory response? — Peptides, 2023. PMID 37068711.
  3. Antibiofilm properties of cathelicidin LL-37: an in-depth review. — World journal of microbiology & biotechnology, 2023. PMID 36781570.
  4. Cathelicidin peptide LL-37: A multifunctional peptide involved in heart disease. — Pharmacological research, 2024. PMID 39615616.
  5. Cathelicidin LL-37 in Health and Diseases of the Oral Cavity. — Biomedicines, 2022. PMID 35625823.
  6. LL-37, a Multi-Faceted Amphipathic Peptide Involved in NETosis. — Cells, 2022. PMID 35954305.

LL-37 FAQ

What is LL-37?
LL-37 is a 37-amino-acid peptide and the only human cathelicidin — a class of host-defense molecules that are part of the innate immune system. It is produced naturally throughout the body and is found in skin, saliva, lungs, and other tissues.[1] Researchers study it because it can both kill microbes directly and communicate with immune cells to modulate the body's defenses.[2]
How does LL-37 work?
LL-37 has an amphipathic (partly water-loving, partly water-repelling) structure that lets it insert into bacterial membranes and destroy them.[3] It also acts as an alarmin — binding to receptors on immune cells like neutrophils and macrophages to trigger or regulate immune responses.[6] Its structural flexibility means it adapts to different environments, giving it a wide range of biological effects.[2]
What is LL-37 used for in research?
Researchers are exploring LL-37 in several areas: fighting antibiotic-resistant biofilm infections,[3] modulating immune and inflammatory responses,[2] promoting wound healing and bone regeneration,[1] understanding oral disease,[5] and investigating its role in cardiovascular conditions like atherosclerosis and thrombosis.[4] All research is preclinical or early-stage.
How is LL-37 dosed in research?
There is no standardized dose — concentrations vary widely across cell culture, animal, and other preclinical models depending on the research goal. Consult the dosage chart on this page for a structured reference of concentrations reported in published literature, and use the calculator to assist with dilution calculations for specific experimental protocols.
How do you reconstitute LL-37?
LL-37 powder is typically dissolved in sterile water or 0.1% acetic acid by gently swirling — not shaking — to preserve the peptide's structure. Once reconstituted, it should be split into single-use aliquots and stored at -80°C for long-term use. Avoid repeated freeze-thaw cycles, which degrade the peptide. Always let vials reach room temperature before opening.
Is LL-37 safe?
LL-37 is an endogenous human peptide, meaning the body produces it naturally, which suggests a baseline level of biological compatibility. However, research also shows it can trigger potent immune events like NETosis[6] and inflammation if overactivated. It is not approved for human therapeutic use. Safety in a research context depends entirely on the specific experimental model, concentration used, and proper handling protocols.