What Is LL-37?

LL-37 is a 37-amino acid cationic host defence peptide (HDP) and the only known member of the cathelicidin family expressed in humans. It is derived from the C-terminal region of the human cathelicidin precursor protein hCAP18 (human cationic antimicrobial protein 18), which is primarily stored in neutrophil granules and secreted by various epithelial cells, including those of the skin, lungs, and gastrointestinal tract. LL-37 is considered a component of the innate immune system and is investigated for its multifunctional roles in host defence biology.

Research-grade LL-37 is supplied by TrueCanPeptides for qualified laboratory use. This compound is not approved for therapeutic application and is intended strictly for scientific investigation.

Mechanism of Action — Research Context

LL-37 is a cationic amphipathic peptide, meaning it carries a positive charge and has both hydrophilic and hydrophobic regions — structural characteristics that are studied in relation to its interactions with negatively charged microbial membranes. In vitro research has examined LL-37’s ability to disrupt bacterial membrane integrity through membrane permeabilisation mechanisms, making it a frequently cited tool compound in antimicrobial peptide research.

Beyond direct antimicrobial activity in experimental models, LL-37 is studied for its immunomodulatory properties. Preclinical research has examined its interactions with G protein-coupled receptors (including FPRL1/FPR2), chemokine induction, and neutrophil, macrophage, and dendritic cell activation in immune biology settings.

Research Applications

• Antimicrobial peptide (AMP) research: LL-37 is a reference compound in studies examining host defence peptide mechanisms, membrane disruption, and bacterial killing in vitro.
• Innate immunity biology: Researchers study LL-37 in the context of innate immune activation, cytokine induction, and epithelial barrier function in cell culture and animal models.
• Wound biology research: LL-37 has been investigated in cell migration and wound healing model systems, studying its effects on keratinocyte and fibroblast behaviour in vitro.
• Inflammatory signalling: Due to its ability to modulate toll-like receptor signalling and cytokine expression, LL-37 is used in research on inflammatory pathway regulation.
• Biofilm research: LL-37 has been studied in preclinical models examining bacterial biofilm disruption, with relevance to chronic infection biology research.

View LL-37 5mg — Research Grade

Storage & Handling

LL-37 is a cationic peptide with sensitivity to degradation by serum proteases and environmental conditions. Handle with standard peptide laboratory precautions:

• Store lyophilised powder at −20°C in sealed, desiccated containers protected from light and humidity
• Reconstitute with sterile water or appropriate low-salt buffer; LL-37 may aggregate at higher salt concentrations depending on conditions
• Use freshly prepared solutions for membrane disruption assays where possible
• Store reconstituted peptide at 4°C; avoid extended storage of aqueous preparations
• Aliquot for repeated use to prevent freeze-thaw cycle degradation

Review our Peptide Storage Guide for comprehensive guidance and see our Quality & Purity standards.

Related Research

LL-37 is part of the broader antimicrobial and host defence peptide (HDP) research space. Researchers investigating immune and defence peptides may find related context in the literature on Thymosin Alpha-1, another immune biology compound studied in innate immunity contexts. Cathelicidin and defensin research often intersect, with LL-37 cited alongside beta-defensins in skin barrier immunity studies. The peptide is also referenced in studies examining vitamin D–cathelicidin axis biology.

Explore the full Research Hub or start with What Are Peptides? for foundational context.

⚠️ Research Use Only: All content on this page is intended strictly for educational and informational purposes. This compound is not approved by Health Canada or any regulatory agency for human therapeutic use. TrueCanPeptides supplies research-grade compounds to qualified researchers only. This is not medical advice. Do not use any information here for self-administration, diagnosis, or treatment. Consult a licensed healthcare professional for any medical concerns.

See also: What is Thymosin Alpha-1?

See also: What is ARA-290?

LL-37 and the Cathelicidin Family

LL-37 is the only known human cathelicidin antimicrobial peptide (AMP). It is generated from the precursor protein hCAP-18 (human cationic antimicrobial protein 18) by proteolytic cleavage of the C-terminal cathelin domain. The name “LL-37” reflects its structure: it begins with two leucine residues (LL) and is 37 amino acids long. LL-37 is expressed in neutrophils, mast cells, NK cells, epithelial cells (skin, gut, lung), and monocytes, and is released at sites of infection and inflammation.

Structure and Chemistry

• Sequence: LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
• Amino acids: 37
• Molecular weight: ~4,493 Da
• Secondary structure: Forms amphipathic alpha-helix in membrane environments — the structural basis for its membrane-disrupting activity
• Charge: Net +6 at physiological pH (cationic) — drives electrostatic interaction with negatively charged bacterial and fungal membranes
• Format: Lyophilized powder

Research Mechanisms

• Membrane disruption (AMPs mechanism): LL-37’s amphipathic helix interacts with the phospholipid bilayers of bacterial membranes, forming pores or disrupting membrane integrity. This mechanism is studied in antimicrobial research using bacterial membrane models and minimum inhibitory concentration (MIC) assays.
• Immunomodulation: LL-37 is a chemoattractant for neutrophils, monocytes, and mast cells via formyl peptide receptor-like 1 (FPRL1). It also promotes dendritic cell maturation and modulates TLR4 signalling.
• Wound biology: LL-37 promotes angiogenesis and epithelial cell migration in wound healing models via interaction with purinergic receptors and EGFR transactivation.
• Biofilm research: LL-37 is studied for its activity against bacterial biofilms — a research area of interest given biofilms’ resistance to conventional approaches.

Storage and Handling

• Store lyophilized at −20°C; protect from moisture and light
• Reconstitute in sterile water; add 0.1% BSA or acetic acid if aggregation is observed
• LL-37 can aggregate at physiological pH and ionic strength — prepare in low-salt buffer or dilute acetic acid stock and dilute into assay buffer
• Post-reconstitution: aliquot immediately; store at −80°C; avoid repeated freeze-thaw

LL-37 is supplied for qualified in vitro laboratory research purposes only. Not for human or animal administration. Not evaluated or approved by Health Canada.

Available: LL-37 5mg from TrueCanPeptides | KPV | Immune & Longevity research compounds