What is LL-37? A Researcher's Guide to the Human Cathelicidin Antimicrobial Peptide

LL-37 is the only member of the cathelicidin family of antimicrobial peptides expressed in humans. It is a 37-amino acid cationic peptide derived from the C-terminus of the human cathelicidin protein hCAP18, and plays a critical role in innate immune defence, wound healing, and immunomodulation. LL-37 has attracted broad research interest due to its multifunctional biological activity across infection, inflammation, and tissue repair.

What is LL-37?

LL-37 is generated by proteolytic cleavage of the precursor protein hCAP18, which is stored in neutrophil granules and secreted by epithelial cells, macrophages, and other immune cells. The name LL-37 refers to its two N-terminal leucine residues and its 37-amino acid length.

It is expressed at sites of infection and inflammation, including skin, respiratory epithelium, and the gastrointestinal tract, where it serves as a first-line defence against pathogens.

Mechanism of Action

LL-37 exerts its biological effects through multiple mechanisms:

• Antimicrobial activity — LL-37 disrupts bacterial, fungal, and viral membranes through electrostatic interaction with negatively charged microbial membranes, leading to membrane permeabilisation and cell death
• Immunomodulation — LL-37 modulates innate and adaptive immune responses by activating toll-like receptor (TLR) signalling, promoting dendritic cell maturation, and regulating cytokine production
• Wound healing — LL-37 promotes keratinocyte migration, angiogenesis, and re-epithelialisation through receptor-mediated signalling (including EGFR and FPRL1/FPR2)
• Anti-biofilm activity — LL-37 disrupts bacterial biofilm formation, an area of significant research interest for chronic infection models

Why LL-37 is of Research Interest

LL-37’s role at the intersection of innate immunity, inflammation, and tissue repair makes it a uniquely versatile research compound. Key areas of ongoing research include:

• Antimicrobial and anti-biofilm research
• Innate immune signalling and TLR modulation
• Wound healing and skin repair models
• Inflammatory skin conditions (psoriasis, rosacea models)
• Respiratory infection and lung defence research
• Cancer biology (LL-37 has both pro- and anti-tumour effects depending on context)
• Autoimmune disease models

Sourcing LL-37 for Research

Research-grade LL-37 should be sourced from suppliers providing batch-specific Certificates of Analysis (CoA) confirming purity (>98%), identity, and potency. Lyophilised formats offer optimal stability for laboratory storage.

At Aura Peptides, our LL-37 is supplied as a research-grade lyophilised peptide with full CoA documentation, available as single vials or in 10x bulk packs for high-volume research programmes.

For research purposes only. Not intended for human or veterinary use.