LL-37: Mechanism, Handling & Research Guide
Also known as: LL-37, Cathelicidin, CAP-18 (37), hCAP18 C-terminal peptide, Cathelicidin antimicrobial peptide (CAMP)
What is LL-37?
LL-37, also known as cathelicidin, is a 37-amino acid cationic antimicrobial peptide (AMP) derived from the C-terminal cleavage of human cathelicidin precursor protein hCAP18. It is the only cathelicidin-derived AMP found in humans and is expressed by neutrophils, epithelial cells, and macrophages. LL-37 kills pathogens through electrostatic interaction with negatively charged microbial membranes, forming toroidal pores that compromise membrane integrity. Beyond direct antimicrobial activity, it modulates innate immunity by acting as a chemoattractant, promoting angiogenesis, and neutralizing bacterial endotoxin (LPS). Research by Zanetti (2004) in Journal of Leukocyte Biology provided a comprehensive characterization of cathelicidin biology and LL-37's multifunctional role in innate defense. Studies in The Journal of Immunology demonstrated that LL-37 exhibited broad-spectrum activity against gram-positive bacteria, gram-negative bacteria, fungi, and enveloped viruses, with minimum inhibitory concentrations in the low micromolar range. Heilborn et al. published findings in Journal of Investigative Dermatology showing that LL-37 expression was significantly reduced in chronic wound beds, and exogenous application promoted re-epithelialization in wound models. Compared to other antimicrobial peptides like defensins (HBD-1, HBD-2), LL-37 has a broader spectrum of activity and more pronounced immunomodulatory effects. Unlike conventional antibiotics, LL-37's membrane-disrupting mechanism makes resistance development unlikely, an increasingly important consideration in antimicrobial research. Store lyophilized LL-37 at -20°C, protected from moisture. Reconstitute with sterile bacteriostatic water and keep at 2-8°C, using within 3 weeks due to potential aggregation. LL-37 is studied by infectious disease researchers, wound healing scientists, immunologists, and antimicrobial resistance specialists investigating peptide-based alternatives to conventional antibiotics.
LL-37 Research Applications
In published and preclinical research, LL-37 has been studied across the following areas:
- Antimicrobial activity against bacteria, fungi, viruses
- Inflammatory response modulation
- ECM-repair and tissue-regeneration research
- Cancer immunotherapy adjuvant research
LL-37 in Research: Study Context
The published literature characterizes LL-37 as the only human cathelicidin-derived antimicrobial peptide, a 37-residue cationic amphipathic alpha-helix released from the hCAP18 precursor and expressed by neutrophils, epithelial cells, and other leukocytes. Comprehensive reviews (Durr, Sudheendra & Ramamoorthy, Biochim Biophys Acta 2006) describe its broad-spectrum membrane-disrupting activity against bacteria, fungi, and enveloped viruses, plus immunomodulatory roles including chemotaxis, LPS neutralization, and modulation of innate-immune signaling. For laboratory research use only; LL-37 is not FDA-approved and no human concentration is established. Reconstitute the lyophilized powder with bacteriostatic water to a defined working concentration (e.g., 2.5 mg/mL for a 5 mg vial) for in-vitro assays, note its tendency to aggregate, reference the primary literature, and document the lot-specific COA.
How LL-37 Compares
Researchers frequently evaluate LL-37 alongside related compounds:
- LL-37 vs KPV — KPV is a tripeptide studied for intracellular NF-kB-directed anti-inflammatory effects, while LL-37 is a large membrane-active peptide that directly kills microbes; the contrast is direct microbicidal action versus signaling modulation.
- LL-37 vs Thymosin Alpha-1 — Thymosin Alpha-1 enhances adaptive immunity by promoting T-cell maturation, whereas LL-37 is a direct-acting innate-immune antimicrobial; researchers pair them to study innate-adaptive cooperation.