What Is LL-37 (CAP-18)?

LL-37 is the only known human cathelicidin, which is a large protein family with diverse function. These peptides, which are primarily found in macrophages and polymorphonuclear leukocytes (both types of white blood cell), are important for killing bacteria, but have been found to have other dramatic effects as well. The entire class is often referred to as antimicrobial peptides (AMPs). LL-37 has been found to play important roles in autoimmune disease, cancer, and wound healing.

LL-37 Structure

Sequence: -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 Molecular Formula: C205H340N60O53 Molecular Weight: 4493.342 g/mol PubChem CID: 16198951 vCAS Number: 154947-66-7 Synonyms: CAP-18, Cathelicidin, antibacterial peptide LL-37

LL-37 Research

LL-37 and Inflammatory Diseases

LL-37, while primarily billed as an antimicrobial peptide, actually plays a role in a number of inflammatory diseases such as psoriasis, lupus, rheumatoid arthritis, and atherosclerosis. Depending on the local inflammatory environment and the particular cells involved, LL-37 has several different immune system modulating behaviors. It has been found to:

Interestingly, LL-37 does not affect the immune system in the same way all of the time. Research in cell culture has shown that the inflammatory environment affects how cells of the immune system respond to LL-37. T-cells, for instance, will increase their inflammatory actions in response to LL-37 when they are not activated but decrease inflammatory action when already activated[2]. It appears that LL-37 has potent homeostatic effects, helping to balance the immune response and prevent it from becoming overactive in the setting of infection. These findings would suggest that LL-37 could play a role in helping to regulate the unchecked inflammation of autoimmune diseases. This may explain why there has been a strong correlation between LL-37 levels and autoimmune disease. It was previously thought that LL-37 might be causing autoimmune inflammation, but more recent evidence suggests that high levels of LL-37 in autoimmune disease may actually be preventing more fulminant inflammation.

LL-37 Is a Potent Antimicrobial

LL-37 is part of the innate immune system and as such is one of the first pieces of the immune system to be activated during infection. Research in skin infections suggests that normal skin has very low levels of LL-37 but that the peptide accumulates rapidly in the presence of invading pathogens. The peptide has been shown to work in tandem with other proteins, like human beta-defensin 2 to combat infection[3].

LL-37 primarily works by binding to bacterial lipopolysaccharide (LPS), a major component of the outer membrane of gram-negative bacteria. LPS is a critical component of membrane integrity in these bacteria. The ability of LL-37 to bind to and interfere with LPS means it is exceptionally deadly to certain bacteria. There is interest in using the peptide exogenously to treat serious bacterial infections in people[4].

Despite the fact that LL-37 acts on the cell membrane components of gram-negative bacteria, it still has potent gram-positive effects as well. This could make it a beneficial treatment for staph infections and other serious bacteria. In vitro research indicates that LL-37 enhances the effects of lysozyme, an enzyme responsible for the destruction of gram positive bacteria like Staph aureus[5].

LL-37 and Lung Disease

LPS, as mentioned above, is not unique to bacterial cell walls. It is found in a number of different organisms and, in some cases, becomes airborne when an environment is contaminated by mold or other fungi. When LPS is inhaled, normal lung tissue responds by producing. Unfortunately, the response is often inadequate to prevent toxic dust syndrome and the pathogenesis of respiratory diseases like asthma, COPD, and more. Research into the use of LL-37 as an inhaled treatment for toxic dust syndrome is currently under way[6].

One of the interesting findings of research into the effects of LL-37 on lung disease is that the peptide promotes epithelial cell proliferation and wound closure. It appears that one of the primary properties of LL-37, at least in the lungs, is to attract airway epithelial cells to the site of injury and promote both wound healing and the growth of blood vessels necessary for providing nutrients to the new tissue. It seems that LL-37 is an important homeostatic regulator in the airways just as it has been found to be a homeostatic regulator of immune function[7].

Understanding LL-37 in Arthritis

Research in rats indicates that LL-37 is found in high concentrations in joints affected by rheumatoid arthritis. In particular, the peptide appears to be associated with the pathological events of arthritis. It isn’t clear, however, if the peptide is causative or its up-regulation in these joints is a part of the body’s attempt to control the pathological process[8]. Several things, however, suggest that LL-37 is beneficial in inflammation and not causative.

First, there is no evidence that LL-37 or any other cathelicidin is involved in the pathogenesis of inflammatory disease. This does not rule the peptide out as being causative, the but evidence weighs pretty heavily against that being the case. In particular, LL-37 deficiency does not affect outcomes in animal models of arthritis or lupus. In other words, animals without LL-37 experience the same pathological progression as animals who have the peptide. Based on these findings, scientists have suggested that reactivity against cathelicidins in arthritis is likely an epiphenomenon that results from extensive over-expression of the peptide in inflamed tissues[9]. In other words, it is incidental.

Research in mouse models of arthritis indicate that peptides derived from LL-37 confer protection against collagen damage that often occurs in inflammatory arthritis. Administration of these peptides directly to affected joints decreases the severity of disease as well as serum levels of antibody against type II collagens[10]. Based on this study, it is reasonable to speculate that LL-37 probably has protective activity in arthritis, which could explain its high concentrations in tissues with substantial inflammation. This speculation is supported by the fact that LL-37 and its derivatives have been shown to regulate inflammation caused by interleukin-32, a molecule that has been directly associated with severity of inflammatory arthritis[11].

Arthritis has also been associated with an up-regulation of toll-like receptor 3 in the fibroblasts of synovial fluid, a factor that likely aggravates arthritis by increasing inflammatory cytokine levels[12]. LL-37 has been shown to bind to TLR4 and either promote pro-inflammatory or anti-inflammatory effects. Which it does in the setting of TLR3 up-regulation isn’t clear, but research is ongoing. The idea that it might reduce inflammation selectively is not unreasonable given that LL-37 has been found to selectively reduce pro-inflammatory macrophage responses in the past[13].

LL-37 and the Intestine

Research in cell cultures indicates that LL-37 has several effects in the intestine. First, the peptide increases migration of cells necessary for maintaining the epithelial barrier of the intestine. Second, LL-37 reduces apoptosis in the setting of intestinal inflammation, helping to slow the pathogenesis of a number of inflammatory conditions. Overall, the research indicates that LL-37 may be a useful adjuvant treatment in inflammatory bowel conditions, following intestinal surgery, or in the setting of acute intestinal infections. It may even prove useful as an adjuvant to antibiotic therapy, helping to prevent the GI side effects that often limit oral antibiotic use[14].

LL-37 does not work alone in the intestine, pairing once again with human beta defensin 2 to promote wound healing. Research in cell culture indicates that the peptides work in tandem to both repair and maintain intestinal epithelium while reducing TNF-related cell death[15]. Currently, TNF-alpha inhibitors are a mainstay of treatment for inflammatory bowel conditions. They are effective drugs, but have a number of serious side effects including causing a drastic increase in the risk of serious infection, such as tuberculosis. The development of LL-37-based treatments of inflammatory bowel disease could help to reduce reliance on TNF-alpha inhibitors and improve morbidity and mortality in this patient population.

LL-37 and Intestinal Cancer

Research regarding LL-37 and cancer has produced mixed results, but the peptide appears to be beneficial in the setting of intestinal and gastric cancers, including oral squamous cell carcinoma associated with smoking and tobacco use. Interestingly, these effects appear to be mediated by a vitamin-D dependent pathway, which may explain why taking the vitamin has been previously associated with a reduced risk for GI cancer. It appears that vitamin D induces the anti-cancer activity of tumor-associated macrophages via LL-37[16].

LL-37 and Blood Vessel Growth

LL-37 appears to trigger the synthesis of prostaglandin E2 (PGE2) in endothelial cells. PGE2 is associated with both inflammatory pain and with the growth of blood vessels, but these effects differ based on where the molecule is being expressed. In endothelial cells, PGE2 triggers the development of blood vessels in a process called angiogenesis[17]. This can be both good and bad, depending on the particular setting. The ability to regulate angiogenesis has been the focus of much research in the last several decades because it impacts cancer development, heart disease, stroke outcomes, wound healing, and more. LL-37 activity offers a useful means for probing the angiogenesis pathway as well as a model for potential future interventions to both promote blood vessel growth when needed (e.g. heart disease) and discourage it when it is detrimental (e.g. cancer).

Ongoing LL-37 Research

One of the interesting things about LL-37 is that it has a different structure in humans than in other mammals[18]. These alternative structures result in different functions for the same basic peptide and provide insight into how three-dimensional configuration can impact receptor binding. This feature makes LL-37 of intense interest because it allows scientists to study the impacts of simple amino acid sequence changes on structure and ultimately function. This could inform an entire branch of biochemistry and make it easier for scientists to manipulate protein production to achieve very specific results.

LL-37 exhibits minimal to moderate side effects, low oral and excellent subcutaneous bioavailability in mice. Per kg dosage in mice does not scale to humans. LL-37 for sale at     peptide Review hub is limited to educational and scientific research only, not for human consumption. Only buy LL-37 if you are a licensed researcher.

Article Author

The above literature was researched, edited and organized by Dr. Logan, M.D. Dr. Logan holds a doctorate degree from Case Western Reserve University School of Medicine and a B.S. in molecular biology.

This PRODUCT IS INTENDED AS A RESEARCH CHEMICAL ONLY. This designation allows the use of research chemicals strictly for in vitro testing and laboratory experimentation only. All product information available on this website is for educational purposes only. Bodily introduction of any kind into humans or animals is strictly forbidden by law. This product should only be handled by licensed, qualified professionals. This product is not a drug, food, or cosmetic and may not be misbranded, misused or mislabled as a drug, food or cosmetic.

LL-37 (also known as CAP-18 or Human Cathelicidin LL-37) is one of the most extensively researched antimicrobial peptides in immunology, infectious disease research, wound healing, inflammation biology, gastrointestinal health, and regenerative medicine. Researchers investigate LL-37 because it serves as the only known human cathelicidin and plays a critical role in innate immune defense, tissue repair, and immune-system regulation.

As interest in antimicrobial and immune-regulating peptides continues to grow, researchers frequently compare LL-37 suppliers based on purity, analytical testing, manufacturing standards, pricing, and supplier transparency.

This LL-37 Vendor Price Comparison Guide helps researchers evaluate suppliers using objective criteria including:

• Product Pricing

• Cost Per Milligram

• Product Purity

• Third-Party Testing

• Certificate of Analysis (COA)

• Vendor Reputation

• Customer Reviews

• Shipping Performance

• Product Availability

• Overall Value

Whether you're looking for the lowest-priced LL-37 supplier, the highest-purity research-grade product, or vendors with extensive analytical verification, this guide provides a framework for comparing peptide suppliers.

Explore LL-37 Vendors by Criteria

Most Popular LL-37 Vendors

Compare suppliers frequently selected by immunology, microbiology, and regenerative medicine researchers.

Highest Reviewed LL-37 Vendors

Discover peptide suppliers with strong customer satisfaction and positive marketplace reputations.

Lowest Price LL-37 Vendors

Identify suppliers offering competitive pricing and attractive cost-per-milligram value.

Highest Purity LL-37 Vendors

Review suppliers providing transparent purity verification and analytical testing.

Best Value LL-37 Vendors

Compare pricing, product quality, laboratory testing, and customer support.

Fastest Shipping LL-37 Vendors

Evaluate fulfillment reliability, packaging standards, and shipping performance.

Newly Listed LL-37 Vendors

Explore recently launched suppliers offering LL-37 research peptides.

What Is LL-37?

Overview

LL-37 is the only known human cathelicidin peptide and a key component of the innate immune system.

Researchers investigate LL-37 because of its relationship with:

• Innate immunity

• Antimicrobial defense

• Immune regulation

• Wound healing

• Inflammation control

• Gastrointestinal biology

• Vascular function

• Cellular repair pathways

LL-37 belongs to a broader family of peptides commonly referred to as antimicrobial peptides (AMPs) and has become an important focus of modern immunology research.

Molecular Characteristics

Peptide Information

Researchers evaluating LL-37 products should carefully review molecular specifications and analytical documentation.

Peptide Name

LL-37

Alternative Names

• CAP-18

• Human Cathelicidin

• Cathelicidin

• Antibacterial Peptide LL-37

Amino Acid Sequence

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

Molecular Formula

C205H340N60O53

Molecular Weight

4493.34 g/mol

PubChem CID

16198951

CAS Number

154947-66-7

Classification

Antimicrobial Peptide (AMP)

Research Category

Immunology & Regenerative Research

Why Researchers Compare LL-37 Vendors

Research reproducibility depends heavily on peptide quality and manufacturing consistency.

Differences among suppliers may include:

• Purity levels

• Batch consistency

• Stability testing

• Manufacturing standards

• Product documentation

• Storage conditions

• Shipping quality

• Quality-control procedures

Careful vendor evaluation helps improve laboratory reliability and reproducibility.

How We Compare LL-37 Vendors

Third-Party Laboratory Testing

Independent laboratory testing remains one of the strongest indicators of research-grade quality.

Researchers should prioritize suppliers offering:

• Third-party testing

• Identity verification

• Purity analysis

• Batch-specific reports

Certificate of Analysis (COA)

A quality COA should include:

• Batch number

• Test date

• Purity percentage

• Identity confirmation

• Analytical methodology

Product Purity

Purity remains one of the most important considerations when evaluating peptides.

Higher-purity products generally improve consistency and reproducibility.

Cost Per Milligram

Comparing product prices alone can be misleading.

Cost Per Milligram Formula

Product Price ÷ Total Milligrams = Cost Per Milligram

This formula provides a more accurate comparison between suppliers.

Customer Reviews

Customer experiences frequently provide insight regarding:

• Product consistency

• Shipping reliability

• Packaging standards

• Customer service

• Purchasing experience

Vendor Reputation

Established peptide suppliers often demonstrate:

• Strong quality-control standards

• Transparent testing procedures

• Reliable inventory availability

• Positive customer satisfaction

Current Research & Evidence

Antimicrobial Research

One of the primary areas of LL-37 research involves antimicrobial defense.

Researchers continue investigating pathways involving:

• Bacterial recognition

• Pathogen defense systems

• Innate immune responses

• Host-defense mechanisms

This remains the most active area of LL-37 research.

Innate Immunity Research

LL-37 serves as one of the body's first lines of defense against invading microorganisms.

Researchers study its role in:

• Immune surveillance

• Host defense

• Immune-cell communication

• Early inflammatory signaling

These investigations continue to expand understanding of innate immunity.

Key Findings on LL-37 Research

Inflammation Research

Researchers have discovered that LL-37 exhibits complex and context-dependent effects on inflammatory pathways.

Areas of investigation include:

• Immune regulation

• Cytokine signaling

• Inflammatory homeostasis

• Autoimmune disease mechanisms

This remains one of the most intriguing aspects of LL-37 biology.

Autoimmune Disease Research

Studies continue evaluating LL-37 in models involving:

• Psoriasis

• Lupus

• Rheumatoid arthritis

• Chronic inflammatory disorders

Researchers are particularly interested in its apparent role as an immune-system regulator rather than a purely pro-inflammatory factor.

Wound Healing Research

LL-37 has attracted substantial attention because of its relationship with tissue repair and regeneration.

Scientists investigate pathways involving:

• Cell migration

• Tissue remodeling

• Epithelial repair

• Regenerative signaling

This remains a major area of regenerative medicine research.

Skin Research

Researchers continue studying LL-37 in relation to:

• Cutaneous immunity

• Barrier protection

• Wound closure

• Skin-repair pathways

The peptide appears to play an important role in maintaining healthy skin responses.

Lung Research

Research has examined LL-37 because of its relationship with:

• Airway epithelial integrity

• Respiratory immune responses

• Lung tissue repair

• Pulmonary inflammation

Scientists continue exploring these mechanisms.

Arthritis Research

Investigations involving rheumatoid arthritis and inflammatory joint disorders have focused on:

• Joint inflammation

• Type II collagen pathways

• Synovial tissue responses

• Cytokine regulation

Additional studies remain ongoing.

Gastrointestinal Research

LL-37 has become a significant subject of gastrointestinal research.

Researchers continue investigating:

• Intestinal barrier integrity

• Epithelial repair

• Gastrointestinal inflammation

• Mucosal maintenance

This remains one of the fastest-growing areas of LL-37 investigation.

Inflammatory Bowel Disease Research

Scientists continue evaluating LL-37 because of its apparent relationship with:

• Intestinal inflammation

• Epithelial healing

• Cell survival pathways

• Gastrointestinal immune regulation

Further research remains ongoing.

Cancer Research

Research involving LL-37 and cancer has produced complex results that vary by tissue type and disease model.

Areas of investigation include:

• Tumor biology

• Immune surveillance

• Angiogenesis

• Tumor-associated macrophage activity

Additional studies continue to explore these interactions.

Angiogenesis Research

One of the most studied properties of LL-37 involves blood-vessel formation.

Researchers investigate pathways related to:

• Endothelial-cell signaling

• Vascular development

• Tissue perfusion

• Wound-repair processes

This research may contribute to a broader understanding of regenerative biology.

Why Researchers Study LL-37

LL-37 remains unique because it influences multiple biological systems simultaneously.

Common areas of investigation include:

• Immunology

• Microbiology

• Infectious disease research

• Gastrointestinal biology

• Dermatology

• Autoimmune disease research

• Regenerative medicine

• Vascular biology

Few antimicrobial peptides possess such broad scientific relevance.

Research Limitations

Most findings involving LL-37 originate from:

• Cell-culture studies

• Animal models

• Laboratory investigations

• Early-stage translational research

Additional studies remain necessary to fully characterize biological mechanisms and long-term effects.

Research findings should not be interpreted as evidence of approved therapeutic applications.

Product Quality & Analytical Testing

Why Testing Matters

Research-grade LL-37 products should undergo testing to verify:

• Identity

• Purity

• Stability

• Potency

• Batch consistency

Common Testing Methods

High-Performance Liquid Chromatography (HPLC)

Used to assess purity and identify impurities.

Mass Spectrometry (MS)

Used to verify molecular identity and composition.

Identity Verification Testing

Confirms peptide authenticity.

Stability Testing

Measures peptide integrity under storage conditions.

Batch Consistency Testing

Evaluates reproducibility across manufacturing lots.

Understanding LL-37 Pricing

Several factors influence supplier pricing.

Product Purity

Higher-purity preparations often command premium pricing.

Peptide Complexity

LL-37 is a relatively large peptide that can require more sophisticated manufacturing methods.

Analytical Verification

Comprehensive testing programs improve transparency but increase production costs.

Research Demand

Growing interest in antimicrobial peptides and regenerative biology continues to drive demand.

Vendor Reputation

Trusted suppliers often charge more due to stronger quality-assurance systems.

LL-37 Vendor Evaluation Checklist

Quality Verification

✅ Third-party testing available

✅ Certificate of Analysis provided

✅ Identity verification documented

✅ Purity information disclosed

✅ Batch-specific testing available

Vendor Reliability

✅ Positive customer reviews

✅ Transparent company information

✅ Responsive customer support

✅ Reliable inventory availability

Purchasing Experience

✅ Secure checkout process

✅ Shipment tracking available

✅ Clear refund policies

✅ Reliable order fulfillment

Red Flags When Comparing Vendors

Testing Concerns

❌ No third-party testing

❌ Missing COAs

❌ Unverified purity claims

❌ Outdated laboratory reports

Transparency Issues

❌ Hidden product specifications

❌ Missing batch information

❌ Limited documentation

❌ No company contact information

Service Problems

❌ Frequent stock shortages

❌ Poor communication

❌ Negative customer reviews

❌ Unclear shipping policies

Frequently Asked Questions

What is LL-37?

LL-37 is the only known human cathelicidin peptide and a major component of the innate immune system involved in antimicrobial defense, tissue repair, and immune regulation.

What is LL-37 used for in research?

Researchers investigate LL-37 in studies involving antimicrobial activity, innate immunity, wound healing, autoimmune diseases, inflammatory bowel disease, lung biology, angiogenesis, gastrointestinal health, and regenerative medicine.

Why compare LL-37 vendors?

Purity, analytical testing, documentation quality, pricing, and supplier reliability can vary substantially among vendors.

What should researchers review before purchasing?

Researchers should evaluate:

• Certificate of Analysis (COA)

• Third-party testing

• Purity verification

• Identity confirmation

• Vendor reputation

• Customer reviews

Why is third-party testing important?

Independent testing helps verify peptide identity, purity, and consistency while improving transparency.

Is the cheapest supplier always the best option?

No. Product quality, testing standards, laboratory verification, and supplier reliability are often more important than price alone.

How often should vendor comparisons be updated?

Pricing, laboratory reports, inventory levels, and supplier policies can change frequently and should be reviewed regularly.

Final Thoughts

LL-37 remains one of the most important antimicrobial peptides in modern immunology because of its involvement in innate immunity, antimicrobial defense, inflammation regulation, wound healing, angiogenesis, gastrointestinal health, and tissue repair pathways. Ongoing investigations continue exploring its role in autoimmune diseases, respiratory health, regenerative medicine, and host-defense mechanisms.

When comparing LL-37 vendors, researchers should prioritize purity verification, third-party testing, Certificate of Analysis availability, supplier reputation, and overall value rather than focusing exclusively on cost. A structured vendor-comparison process can help identify suppliers capable of meeting rigorous research-quality standards.