LL-37
Cathelicidin antimicrobial peptide
A human cathelicidin-derived antimicrobial peptide studied in immunology and tissue-repair research.
Also referenced as: Cathelicidin
Overview
LL-37 is a naturally occurring human antimicrobial peptide, the active fragment released from the C-terminal region of the human cathelicidin precursor protein hCAP18. It is part of the innate immune system and is expressed by neutrophils and various epithelial cells.
At a glance
What LL-37 does
LL-37 is the only human cathelicidin antimicrobial peptide, a 37-residue amphipathic helix released from a precursor protein by immune and epithelial cells. Its foundational action is direct, broad-spectrum antimicrobial killing: the cationic, amphipathic peptide is drawn to the negatively charged membranes of bacteria, fungi, and enveloped viruses, then inserts into and disrupts those membranes (described by carpet, toroidal-pore, and detergent-like micellization models), causing leakage and microbial death. Because this is a physical membrane attack, resistance is harder to develop than with conventional antibiotics.
Beyond killing microbes, LL-37 is a multifunctional immunomodulator and repair peptide. It neutralizes bacterial endotoxin (LPS), inhibits biofilm formation, and shapes the immune response by recruiting and activating neutrophils, macrophages, and other cells, tuning cytokine output, and influencing antigen presentation. In wound-healing research it promotes keratinocyte migration and proliferation, drives angiogenesis (partly via VEGF upregulation and, notably, by acting as an agonist at the IGF-1 receptor), and modulates fibroblast activity, all of which support re-epithelialization and tissue repair.
Most of the mechanistic and efficacy data come from in-vitro assays and animal models, with endogenous LL-37 biology being well studied in human immunity. However, LL-37 has a dual nature: at high levels or in the wrong context it can be pro-inflammatory and has been linked to autoimmune and inflammatory conditions such as psoriasis and rosacea. Administering it as a therapeutic remains investigational, and controlled human trials of exogenous LL-37 are limited.
Effects reported in research
- Directly kills bacteria, fungi, and enveloped viruses by electrostatically binding and disrupting their membranes (in-vitro; core function).
- Neutralizes bacterial lipopolysaccharide (LPS) endotoxin, blunting endotoxin-driven inflammation (in-vitro/animal).
- Inhibits microbial biofilm formation and enhances bacterial phagocytosis (in-vitro).
- Recruits and activates neutrophils and macrophages and modulates cytokine signaling as an immunomodulator (in-vitro/animal).
- Promotes keratinocyte migration and proliferation to support wound re-epithelialization (in-vitro/animal).
- Drives angiogenesis, including via VEGF upregulation and agonism at the IGF-1 receptor (in-vitro/animal).
- Can be pro-inflammatory in excess and is implicated in psoriasis, rosacea, and autoimmune inflammation (a dual, context-dependent effect).
- Human clinical evidence for administered LL-37 is limited; most efficacy data are preclinical.
Effects listed reflect findings reported in the research literature — many in animal or in-vitro models. Listing an effect is not a claim of efficacy or a therapeutic indication in humans.
Mechanism of action
LL-37 is a cationic, amphipathic host-defense peptide that can disrupt microbial membranes, giving it broad antimicrobial activity. Beyond direct killing, it has immunomodulatory roles, including chemotactic effects on immune cells, modulation of inflammatory signaling, and reported influence on angiogenesis and wound healing. These roles are documented in in-vitro and animal studies as part of innate immunity.
Mechanistic description reflects published research-literature understanding. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
What it's studied for
Research contexts in which LL-37 appears in the literature. Listing a research area is not a claim of efficacy or a therapeutic indication.
Key characteristics
- A naturally occurring 37-residue human cathelicidin peptide
- Cationic and amphipathic structure underlies membrane-disrupting antimicrobial action
- Has dual antimicrobial and immunomodulatory functions
- Extensively studied as part of the innate immune system
- Not an approved therapeutic peptide
Reported research dosing reference only
Educational reference, not dosing guidance. The figures below summarize amounts reported in published research and research-community protocols, provided for educational and research context only. They are not medical advice, not a recommendation, and not instructions for human use. LL-37 is a research compound.
LL-37 research is largely in vitro and mechanistic (e.g. minimum inhibitory concentrations against microbes), so there is no established human research-dosing standard; reported figures are experimental concentrations. These are research-context reference figures only, not dosing guidance.
- In vitro antimicrobial assays: activity typically characterized by micromolar or microgram/mL concentrations (assay-specific)
Larger cationic peptide (37 aa, MW ~4493 Da). Evidence base is preclinical; no confirmed human systemic dosing standard.
How it compares
LL-37 is unique in this group as a natural host-defense peptide combining direct antimicrobial activity with immune modulation, rather than being a synthetic repair-focused peptide.
Commonly studied alongside
Compounds frequently researched together with LL-37 in the literature. Cross-referenced for research context — not a usage or combination recommendation.
Compare and calculate
Side-by-side pages for the pairings the literature already documents for LL-37, plus the unit-conversion reference for a reconstituted vial. Factual comparisons of documented characteristics — not a recommendation to combine or use any compound.
Handling & Stability
Lyophilized peptides are stored cold, protected from light, and reconstituted only at the time of intended in-vitro work.
- Avoid repeated freeze-thaw cycles
- Verify supplier lot and Certificate of Analysis
- Follow institutional lab-safety protocols
Analytical & COA Concepts
Reputable research suppliers publish a third-party Certificate of Analysis per batch. Key analytical concepts referenced in COAs include:
Category Context
LL-37 sits in the Healing & Recovery area of the PeptiDex library.
- Entry type: Research compound reference
- Healing & Recovery category hub →
- Browse the full library →
- Glossary of terms →
Research reference
No supplier listing is attached to this profile. The cited study describes its own formulation and population.
Read the evidence guide →Frequently asked questions
What is LL-37?
LL-37 is the sole human cathelicidin antimicrobial peptide, a 37-amino-acid amphipathic alpha-helical peptide released from the C-terminal region of the hCAP18 precursor. It is named for its two leading leucine residues and its length. It functions in the innate immune system as a first-line defense at sites of infection, inflammation, and wounds.
What is LL-37 studied for?
Research examines LL-37 for direct antimicrobial activity against bacteria, and for antiviral, immunomodulatory, angiogenic, and wound-healing roles. Multiple patents describe LL-37 and its derivatives for wound healing. It is also studied in the context of inflammatory and autoimmune conditions, where it can present nucleic acids to immune receptors.
How does LL-37 kill microbes?
As a cationic, amphipathic alpha-helix, LL-37 interacts with and disrupts negatively charged microbial membranes, permeabilizing them. This membrane-targeting mechanism makes broad resistance harder to develop than with conventional antibiotics, which is a key reason it is studied as an antimicrobial-peptide template.
Does LL-37 have effects beyond killing bacteria?
Yes. Beyond bactericidal action it has reported antiviral and antitumor activity and acts as an immunomodulator, influencing chemotaxis, angiogenesis, and wound repair. This dual antimicrobial and immunoregulatory profile is why it appears in both anti-infective and tissue-repair research.
Is LL-37 an approved drug?
No. LL-37 is an endogenous human peptide studied as a research compound and antimicrobial-peptide template; it is not an approved therapeutic. Its evidence base is preclinical and mechanistic. It is sometimes discussed alongside KPV in immune-modulation and antimicrobial research.
Answers are educational summaries of research-literature context and do not constitute medical advice. See the Research Library, COA guide, and Storage & Handling guide for more.
References
Publications indexed in PubMed and linked to this profile, including original studies and reviews. Publication labels reflect PubMed indexing, not evidence strength. Listing a study records that it exists and is indexed — it is not a claim of efficacy, a therapeutic indication, or an endorsement of its conclusions. Much of this literature is preclinical (in-vitro or animal-model).
- LL-37: Cathelicidin-related antimicrobial peptide with pleiotropic activity
Review · Citation and indexing details
- Unique features of human cathelicidin LL-37
Review · Citation and indexing details
Bibliographic metadata refreshed from PubMed on 2026-09-20. This checks the record identity and metadata; it is not a new review of every scientific claim. A reference may concern a related molecule or formulation: read its methods and the context above. See the editorial policy.