LL-37 Ireland | Buy Research-Grade Antimicrobial Peptide | ≥99% Purity

LL-37 is a synthetic cathelicidin-derived antimicrobial peptide and the only member of the human cathelicidin family — a 37 amino acid cationic host defence peptide produced naturally by neutrophils, epithelial cells, and macrophages as a frontline component of innate immune defence — making it one of the most multifunctional and extensively researched host defence peptides available to laboratories in Ireland, combining direct antimicrobial activity against bacteria, fungi, and viruses with potent immunomodulatory, wound healing, and anti-biofilm properties that extend its research relevance far beyond classical antimicrobial biology. Researchers and institutions across Ireland can source verified, research-grade LL-37 directly from our Irish peptide supply, with domestic-speed dispatch and complete batch documentation.

✅ ≥99% Purity — HPLC & Mass Spectrometry Verified

✅ Batch-Specific Certificate of Analysis (CoA) Included

✅ Sterile Lyophilised Powder | GMP Manufactured

✅ Fast Dispatch to Ireland | Peptides Ireland Stock

What Is LL-37?

LL-37 is the sole human cathelicidin antimicrobial peptide — formally designated hCAP-18/LL-37 in its full-length precursor form — consisting of 37 amino acids (Leu-Leu-Gly-Asp-Phe-Phe-Arg-Lys-Ser-Lys-Glu-Lys-Ile-Gly-Lys-Glu-Phe-Lys-Arg-Ile-Val-Gln-Arg-Ile-Lys-Asp-Phe-Leu-Arg-Asn-Leu-Val-Pro-Arg-Thr-Glu-Ser) cleaved from the C-terminal domain of the 18 kDa precursor protein hCAP-18 by serine protease processing. The designation LL-37 reflects both its length and the two leucine residues at its N-terminus — a naming convention that captures the structural identity of this peptide as the biologically active cathelicidin fragment released from its precursor upon cellular activation.

LL-37 is produced and stored in the granules of neutrophils — released rapidly upon neutrophil activation at sites of infection or injury — and is also expressed and secreted by epithelial cells lining the skin, respiratory tract, gastrointestinal tract, and urogenital system, as well as by macrophages, mast cells, and natural killer cells. This broad cellular expression pattern reflects LL-37’s role as a constitutive and inducible component of the innate immune system — present at barrier surfaces as a first-line defence and rapidly upregulated in response to microbial challenge, inflammatory signals, and tissue damage. Vitamin D signalling is one of the most important physiological regulators of LL-37 expression — with the active vitamin D metabolite 1,25-dihydroxyvitamin D3 directly driving cathelicidin gene transcription through vitamin D response elements in the CAMP gene promoter, establishing a well-characterised link between vitamin D status and innate antimicrobial defence capacity.

The structural basis of LL-37’s biological activity is its amphipathic alpha-helical conformation — adopted upon interaction with lipid membranes and providing a structure with a hydrophobic face that inserts into and disrupts microbial membranes and a positively charged face that drives electrostatic attraction to negatively charged bacterial, fungal, and viral membrane surfaces. This amphipathic helix is the molecular architecture underlying LL-37’s membrane-disrupting antimicrobial mechanism — and the same structural features that drive membrane interaction also underlie many of its immunomodulatory and receptor-engaging properties in host cell biology.

Beyond its direct antimicrobial function, LL-37 engages multiple host cell receptors — including formyl peptide receptor-like 1 (FPRL1), P2X7 purinergic receptor, epidermal growth factor receptor (EGFR), and toll-like receptors — producing a remarkably diverse range of immunomodulatory, pro-angiogenic, wound healing, and cell signalling effects that have established LL-37 as a multifunctional host defence molecule whose biological relevance extends far beyond direct pathogen killing into the broader biology of inflammation, tissue repair, and immune regulation.

What Does LL-37 Do in Research?

In controlled laboratory and pre-clinical settings, LL-37 is studied across a wide range of antimicrobial biology, immunology, wound healing, and host defence research applications:

Antimicrobial Mechanism Research — LL-37’s direct antimicrobial activity against Gram-positive and Gram-negative bacteria, fungi, and enveloped viruses has been extensively characterised — with research examining membrane disruption mechanisms, minimum inhibitory concentrations across pathogen species, structure-activity relationships within the cathelicidin scaffold, and how LL-37’s amphipathic alpha-helical architecture determines pathogen selectivity. Studies have documented LL-37’s activity against clinically significant bacterial species including Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and drug-resistant organisms — making it a research tool of significant interest for studying novel antimicrobial mechanisms in the context of antibiotic resistance research.

Anti-Biofilm Biology Research — One of the most significant and distinctive research areas for LL-37 is its anti-biofilm activity — with studies documenting LL-37’s capacity to inhibit biofilm formation and disrupt established biofilms of multiple bacterial species at concentrations below those required for direct bacterial killing. Biofilm formation is a primary mechanism of antibiotic resistance and chronic infection persistence — and LL-37’s anti-biofilm properties, mediated through interference with quorum sensing signalling and biofilm matrix disruption, make it a particularly important research tool for studying how host defence peptides counter biofilm-related bacterial persistence mechanisms.

Immunomodulatory Biology Research — LL-37 is a potent immunomodulator with documented effects on innate and adaptive immune cell function — including chemotactic recruitment of neutrophils, monocytes, and T cells through FPRL1 receptor engagement, modulation of toll-like receptor signalling and LPS-driven inflammatory responses, and effects on dendritic cell maturation and antigen presentation. Studies have characterised LL-37’s capacity to both amplify and regulate inflammatory responses depending on concentration and cellular context — establishing it as a research tool for studying how host defence peptides shape the inflammatory microenvironment during infection and tissue damage.

Wound Healing and Tissue Repair Research — LL-37 has documented pro-wound healing properties — with studies characterising its effects on keratinocyte migration and proliferation through EGFR transactivation, fibroblast chemotaxis and collagen production, angiogenesis through VEGF pathway stimulation, and re-epithelialisation in wound closure models. These wound healing properties reflect LL-37’s physiological role at epithelial barrier surfaces — where it serves not only as an antimicrobial agent but as a tissue repair signal coordinating the cellular responses that restore barrier integrity following damage.

Antiviral Biology Research — Beyond antibacterial activity, LL-37 has documented antiviral properties against multiple enveloped virus families — with studies examining direct membrane disruption of enveloped virions, inhibition of viral attachment to host cells, and immunomodulatory effects on antiviral innate immune responses. Research has characterised LL-37 activity against respiratory viruses, herpesviruses, and retroviruses — positioning it as a research tool relevant to studying innate antiviral defence mechanisms and host defence peptide antiviral biology.

Vitamin D — Cathelicidin Axis Research — The well-characterised regulation of LL-37 expression by vitamin D signalling has made LL-37 a central research tool for studying the immunological mechanisms through which vitamin D influences innate immune defence. Studies have examined how vitamin D-driven cathelicidin expression affects antimicrobial defence capacity in respiratory epithelium, macrophage antimycobacterial activity, and the epidemiological associations between vitamin D status and susceptibility to infectious diseases — making LL-37 the molecular link between vitamin D biology and innate immune research.

Cancer Biology Research — LL-37 has a complex and context-dependent role in cancer biology — with studies documenting both pro-tumorigenic effects through EGFR activation and angiogenesis stimulation in certain tumour microenvironments and anti-tumour effects through direct cytotoxicity against cancer cell lines and immunostimulatory effects on anti-tumour immune responses. This dual role has generated significant research interest in LL-37 as a tool for studying how host defence peptides interact with the tumour microenvironment — an area with implications for understanding how innate immune molecules influence cancer biology.

Autoimmune and Inflammatory Disease Biology Research — Elevated LL-37 levels have been documented in inflammatory conditions including psoriasis, lupus, and rosacea — with research characterising how LL-37 complexes with self-DNA and self-RNA to activate toll-like receptors and drive type I interferon responses in plasmacytoid dendritic cells, potentially contributing to autoimmune pathology. Studies examining how LL-37 crosses the line from protective innate defence to maladaptive autoimmune activation have important implications for understanding the pathobiology of TLR-driven autoimmune diseases.

Lung and Respiratory Biology Research — LL-37 expression in airway epithelium and its roles in respiratory innate defence have been studied extensively — with research examining LL-37 activity against respiratory pathogens, its effects on airway epithelial cell biology, and its potential role in respiratory conditions including cystic fibrosis — where LL-37 antimicrobial activity is reportedly inhibited by the high salt environment of cystic fibrosis airway secretions, a finding with important implications for understanding innate defence failure in CF lung disease.

Structure-Activity Relationship Research — LL-37’s 37 amino acid sequence has been the subject of extensive structure-activity relationship research — with studies examining truncated fragments, analogues with modified amino acid sequences, and peptides with altered charge or amphipathicity to identify the minimal active sequence and key structural determinants of antimicrobial potency, immunomodulatory activity, and host cell selectivity. This SAR research has informed the development of next-generation host defence peptide research tools based on the cathelicidin scaffold.

What Do Studies Say About LL-37?

LL-37 has accumulated one of the most extensive research literatures of any host defence peptide — spanning antimicrobial biology, immunology, wound healing, cancer research, and autoimmune disease biology across decades of pre-clinical investigation.

Broad-Spectrum Antimicrobial Activity Extensively Documented — Studies have comprehensively characterised LL-37’s antimicrobial activity across bacterial, fungal, and viral pathogens — establishing minimum inhibitory concentrations against a wide range of clinically relevant organisms and documenting the membrane disruption mechanism through biophysical studies. Research has confirmed LL-37’s activity against antibiotic-resistant organisms including MRSA and multidrug-resistant Gram-negative pathogens — establishing its research significance in the context of antimicrobial resistance biology, where novel mechanism-of-action compounds are of intense research interest.

Anti-Biofilm Activity Confirmed in Multiple Pathogen Models — Research has documented LL-37’s capacity to inhibit biofilm formation and disrupt pre-formed biofilms in Pseudomonas aeruginosa, Staphylococcus aureus, and other biofilm-forming pathogens at sub-MIC concentrations — with mechanistic studies characterising interference with quorum sensing through interaction with acyl-homoserine lactone signalling molecules as one mechanism contributing to biofilm inhibition. These anti-biofilm findings are among the most significant in the LL-37 literature given the critical clinical and research importance of biofilm-associated infections.

FPRL1-Mediated Immunomodulation Characterised — Studies have established FPRL1 (formyl peptide receptor-like 1) as a primary receptor mediating LL-37’s chemotactic and immunomodulatory effects on immune cells — with research characterising LL-37-driven neutrophil and monocyte chemotaxis, T cell recruitment, and modulation of dendritic cell function through this receptor. The FPRL1 signalling pathway has been established as a key mechanism through which LL-37 bridges innate antimicrobial defence and adaptive immune cell recruitment — making it important context for interpreting LL-37 immunomodulatory research findings.

EGFR Transactivation and Wound Healing Biology Documented — Research has characterised LL-37’s activation of the epidermal growth factor receptor (EGFR) in keratinocytes — with studies documenting EGFR-dependent keratinocyte migration, proliferation, and wound re-epithelialisation responses driven by LL-37 signalling. This EGFR transactivation mechanism has been identified as a central pathway through which LL-37 promotes wound healing at epithelial barrier surfaces — connecting its antimicrobial and tissue repair functions through a shared receptor biology that has generated significant research interest in the relationship between host defence and wound healing.

Vitamin D Regulation of LL-37 Expression Established — Research has firmly established the vitamin D signalling pathway as a primary regulator of cathelicidin/LL-37 gene expression — with studies characterising the vitamin D response element in the CAMP gene promoter, documenting upregulation of LL-37 expression in immune and epithelial cells following vitamin D receptor activation, and linking vitamin D sufficiency to enhanced innate antimicrobial defence capacity in pre-clinical and epidemiological research. This vitamin D-cathelicidin axis has become one of the most important mechanistic explanations for observed associations between vitamin D status and susceptibility to respiratory and other infectious diseases.

Role in Autoimmune Pathology Characterised — Research has documented LL-37’s role in driving toll-like receptor-mediated autoimmune responses — with studies establishing that LL-37 forms complexes with self-DNA and self-RNA that are internalised by plasmacytoid dendritic cells and activate TLR7 and TLR9 to drive type I interferon production. This mechanism has been characterised as a pathological amplification of normally protective innate signalling in conditions including psoriasis and systemic lupus erythematosus — making LL-37 a research tool of central importance for studying the molecular pathobiology of TLR-driven autoimmune diseases.

Context-Dependent Cancer Biology Documented — Research has characterised LL-37’s complex dual role in cancer biology — with studies documenting pro-tumorigenic effects through EGFR-driven proliferative signalling and angiogenesis stimulation in ovarian, lung, and breast cancer cell models, alongside anti-tumour effects through direct cytotoxicity and immunostimulatory activity in other tumour biology contexts. This context-dependent cancer biology has generated significant research interest in how cathelicidin expression in the tumour microenvironment shapes cancer progression — and has positioned LL-37 as an important research tool for studying the intersection of innate immune biology and tumour biology.

How Does LL-37 Compare to Other Host Defence Peptide Research Compounds?

Feature	LL-37	Defensin HNP-1	Magainin-2	Melittin	Polymyxin B
Origin	Human cathelicidin	Human alpha-defensin	Frog skin AMP	Bee venom AMP	Bacterial-derived antibiotic
Structure	37aa — amphipathic alpha-helix	30aa — beta-sheet — 3 disulphide bonds	23aa — amphipathic helix	26aa — amphipathic helix	Cyclic lipopeptide
Antimicrobial Spectrum	Broad — bacteria, fungi, viruses	Broad — bacteria, fungi, viruses	Broad — bacteria, fungi	Broad — bacteria, fungi	Gram-negative selective
Anti-Biofilm Activity	Strong — documented	Moderate	Moderate	Strong	Limited
Immunomodulatory Activity	Extensive — FPRL1, TLR, EGFR	Moderate — TLR engagement	Limited	Limited	Minimal
Wound Healing Activity	Strong — EGFR transactivation	Moderate	Limited	Limited	None documented
Autoimmune Research Relevance	High — TLR/IFN axis, psoriasis, lupus	Moderate	Low	Low	None
Human Physiological Relevance	Highest — only human cathelicidin	High — human defensin	Low — non-human	Low — non-human	Low — bacterial origin
Research Profile	Extensively studied	Well-documented	Well-documented	Well-documented	Extensively studied

Product Specifications

Parameter	Detail
Name	LL-37 (Human Cathelicidin Antimicrobial Peptide)
Full Designation	hCAP-18/LL-37 active fragment
Length	37 amino acids
Structure	Amphipathic alpha-helix — cationic
Natural Source	Neutrophils, epithelial cells, macrophages — innate immune
Primary Targets	Bacterial/fungal/viral membranes + FPRL1, EGFR, P2X7, TLRs
Key Research Areas	Antimicrobial, anti-biofilm, immunomodulation, wound healing, autoimmune, cancer biology
Purity	≥99% HPLC & MS Verified
Form	Sterile Lyophilised Powder
Solubility	Sterile water or 0.1% acetic acid water — see reconstitution note
Storage (Powder)	-20°C, protect from light
Storage (Reconstituted)	2–8°C, use within 7 days or aliquot at -80°C
Manufacturing	GMP Manufactured
Intended Use	Research use only

LL-37 Reconstitution — Important Note

LL-37 can be reconstituted in sterile water or 0.1% acetic acid water — the mildly acidic acetic acid solution is recommended when working at lower concentrations to prevent aggregation and ensure complete solubilisation of the cationic peptide. Add diluent slowly down the inside wall of the vial and swirl gently — do not inject directly onto the lyophilised powder and do not vortex or shake vigorously. Prepare a concentrated stock solution and dilute to working concentration in PBS or appropriate cell culture buffer as required by your research protocol. Store reconstituted stock at 2–8°C for short-term use within 7 days, or aliquot into single-use volumes and store at -80°C for longer-term preservation. Use low-binding tubes where possible — cationic peptides including LL-37 can adsorb to standard plastic surfaces at low concentrations. Avoid repeated freeze-thaw cycles.

Acetic Acid Water for peptide reconstitution is available separately in our Ireland research solvent range.

Buy LL-37 in Ireland — What’s Included

Every order of LL-37 in Ireland includes:

✅ Batch-Specific Certificate of Analysis (CoA)

✅ HPLC Chromatogram

✅ Mass Spectrometry Confirmation

✅ Sterility & Endotoxin Testing Report

✅ Reconstitution Protocol

✅ Technical Research Support

Frequently Asked Questions — LL-37 Ireland

Can I Buy LL-37 in Ireland?

Yes — we supply research-grade LL-37 to researchers and institutions across Ireland with fast dispatch and full batch documentation. This compound is supplied strictly for laboratory research purposes only.

What is LL-37 and Why is it Unique Among Human Antimicrobial Peptides?

LL-37 holds a distinctive position in antimicrobial peptide research as the sole human cathelicidin — the only member of the cathelicidin antimicrobial peptide family expressed in humans, making it the primary human representative of this ancient and conserved innate defence peptide class. While other mammals express multiple cathelicidin family members, humans produce only one — hCAP-18/LL-37 — which must therefore cover the full range of cathelicidin-mediated innate defence functions that multiple peptides serve in other species. This singularity makes LL-37 an exceptionally important research compound — it is not one of several human cathelicidins but the human cathelicidin, with research implications spanning antimicrobial defence, immune regulation, wound healing, and inflammatory disease biology that cannot be distributed across a family of related peptides as in other species.

What is the Amphipathic Alpha-Helix and Why Does It Matter for LL-37 Research?

The amphipathic alpha-helix is the structural conformation adopted by LL-37 upon interaction with lipid membranes — and is the molecular architecture underlying virtually all of its biological activities. In this helical conformation, LL-37 arranges its amino acids into a structure with a hydrophobic face on one side of the helix and a positively charged hydrophilic face on the other — a spatial arrangement that drives membrane insertion through the hydrophobic face while the positively charged face provides electrostatic attraction to the negatively charged surfaces of bacterial membranes, fungal membranes, and viral envelopes. This amphipathic architecture is also relevant to LL-37’s interactions with host cell receptors and self-nucleic acids in immunomodulatory contexts — making understanding of the amphipathic helix structure essential for interpreting LL-37 research findings across its diverse biological applications.

How Does LL-37 Differ from Conventional Antibiotics in Research Terms?

LL-37’s mechanism of antimicrobial action is fundamentally distinct from conventional antibiotics in ways that make it an important research tool for studying alternative antimicrobial strategies in the context of rising antibiotic resistance. Conventional antibiotics typically target specific bacterial enzymes or biosynthetic pathways — mechanisms that are vulnerable to resistance development through target mutation or enzyme-mediated drug inactivation. LL-37 acts primarily through direct disruption of the bacterial membrane — a target that is much more difficult for bacteria to modify without catastrophic fitness costs, since the fundamental biophysical properties of bacterial membranes cannot be easily altered through point mutations. This membrane-targeting mechanism, combined with LL-37’s anti-biofilm properties and immunomodulatory effects that can recruit additional immune responses, makes it a research compound of significant interest for studying host defence strategies that may circumvent classical antibiotic resistance mechanisms.

What is the Vitamin D — LL-37 Connection and Why is it Significant in Research?

The regulation of LL-37 expression by vitamin D signalling is one of the most important and well-characterised links between nutritional biology and innate immune function — with direct implications for research into respiratory infection susceptibility, tuberculosis biology, and the immunological mechanisms through which vitamin D status influences infection outcomes. The active vitamin D metabolite 1,25-dihydroxyvitamin D3 directly drives transcription of the CAMP gene — which encodes hCAP-18/LL-37 — through vitamin D response elements in the CAMP promoter, meaning that vitamin D signalling directly controls the production of the body’s primary cathelicidin antimicrobial peptide. Research has characterised this axis in human macrophages, airway epithelial cells, and skin keratinocytes — with studies documenting enhanced LL-37 expression and antimicrobial activity following vitamin D receptor activation. This vitamin D-cathelicidin axis has become the leading mechanistic explanation for epidemiological associations between vitamin D deficiency and increased susceptibility to respiratory infections and tuberculosis, making LL-37 the critical molecular link between these fields.

How is LL-37 Involved in Autoimmune Disease Research?

LL-37’s involvement in autoimmune disease biology represents one of the most scientifically significant aspects of its research profile — illustrating how a molecule evolved for protective innate defence can become pathologically activated in certain disease contexts. In psoriasis, elevated LL-37 levels at inflammatory skin lesions lead to LL-37 forming complexes with self-DNA released from damaged keratinocytes — these LL-37-DNA complexes are internalised by plasmacytoid dendritic cells and activate TLR9, driving type I interferon production and amplifying the inflammatory cascade that characterises psoriatic disease. Similar LL-37-nucleic acid complex formation has been characterised in systemic lupus erythematosus — where LL-37-RNA complexes activate TLR7 in the same manner. This mechanism — whereby LL-37 converts normally non-immunogenic self-nucleic acids into potent TLR activators — has been established as a central pathobiological mechanism in multiple TLR-driven autoimmune conditions, making LL-37 an essential research tool for studying the molecular basis of autoimmune amplification through innate immune pathway dysregulation.

What is LL-37’s Role in Cancer Biology Research?

LL-37’s role in cancer biology is complex, context-dependent, and an area of active and growing research interest. Studies have documented pro-tumorigenic effects of LL-37 in certain cancer cell models — particularly through EGFR transactivation driving proliferative signalling in ovarian, lung, breast, and colon cancer cell lines, and through pro-angiogenic effects via VEGF pathway stimulation that could support tumour vascularisation. At the same time, research has documented direct cytotoxic effects of LL-37 against cancer cell lines through membrane disruption mechanisms similar to its antimicrobial activity, and immunostimulatory effects that could enhance anti-tumour immune responses. The balance between these pro- and anti-tumorigenic effects appears to depend on LL-37 concentration, tumour microenvironment context, and cancer cell type — making LL-37 a valuable research tool for studying how endogenous host defence molecules shape tumour biology, and raising important questions about cathelicidin expression levels as a variable in cancer biology research.

What Purity is Recommended for LL-37 Research?

≥99% purity is strongly recommended for LL-37 antimicrobial assays, immunomodulatory biology studies, receptor binding pharmacology, wound healing research, and pre-clinical in vivo models — where compound purity directly affects the reliability and reproducibility of biological activity measurements. Given LL-37’s potent receptor-engaging and membrane-active properties, even minor peptide impurities can introduce confounding biological signals in sensitive assays. All LL-37 Ireland stock is independently verified to ≥99% purity by HPLC and mass spectrometry.

How Do I Reconstitute LL-37 for Laboratory Use?

Allow the vial to reach room temperature before opening. Add sterile water or 0.1% acetic acid water slowly down the inside wall of the vial — do not inject directly onto the lyophilised powder and do not vortex or shake vigorously. Swirl gently until fully dissolved. Prepare a concentrated stock solution and dilute to working concentration in PBS or appropriate cell culture buffer. Store reconstituted stock at 2–8°C for short-term use within 7 days, or aliquot into single-use volumes and store at -80°C for longer-term preservation. Use low-binding tubes where possible — cationic peptides including LL-37 can adsorb to standard plastic surfaces at low concentrations. Avoid repeated freeze-thaw cycles.

Research Disclaimer

LL-37 is supplied exclusively for legitimate scientific research purposes conducted within licensed laboratory environments. This product is not intended for human consumption, self-administration, or any therapeutic application. It must be handled by qualified researchers in compliance with applicable Irish and EU regulations and institutional ethics guidelines. By purchasing, you confirm that this compound will be used solely for approved in vitro or pre-clinical research purposes.