LL-37 (Cathelicidin)
LL-37 | Cathelicidin | CAP18 | hCAP18
Mechanism of Action
LL-37 is the only human cathelicidin antimicrobial peptide, derived from the C-terminal cleavage of the 18-kDa precursor protein hCAP18 by proteinase 3. It is a 37-amino-acid amphipathic alpha-helical peptide produced by neutrophils, macrophages, epithelial cells, and other cell types as part of the innate immune defense.
LL-37's antimicrobial mechanism involves direct membrane disruption of microbial cells. Its amphipathic structure — with a hydrophobic face and a cationic (positively charged) face — enables it to insert into negatively charged microbial membranes, causing pore formation and cell lysis. It is active against a broad spectrum of Gram-positive and Gram-negative bacteria, fungi, and enveloped viruses. Crucially, LL-37 also disrupts bacterial biofilms at sub-bactericidal concentrations, a property that distinguishes it from many conventional antibiotics.
Beyond direct antimicrobial activity, LL-37 serves as a potent immunomodulator. It recruits immune cells to infection sites by acting as a chemoattractant for neutrophils, monocytes, and T-cells via the formyl peptide receptor-like 1 (FPRL1). It promotes wound healing by stimulating angiogenesis and re-epithelialization. LL-37 also modulates Toll-like receptor signaling, enhancing the immune response to bacterial products while dampening potentially harmful excessive inflammatory responses.
Key Research Findings
- Hancock & Sahl (2006) reviewed antimicrobial peptides including LL-37 as key effectors of innate immunity with direct microbicidal and immunomodulatory functions.
- Overhage et al. (2008) demonstrated LL-37 inhibits Pseudomonas aeruginosa biofilm formation at 0.5 mcg/mL — well below its bactericidal concentration — through interference with quorum sensing.
- Heilborn et al. (2003) showed LL-37 is upregulated during wound healing and promotes re-epithelialization of human skin wounds.
- Vandamme et al. (2012) reviewed LL-37's dual role as antimicrobial agent and wound healing promoter.
References
Dosage in Research
In vitro antimicrobial studies use 1-32 mcg/mL. Anti-biofilm activity observed at 0.5-4 mcg/mL. Wound healing studies in animals use topical application of 10-100 mcg/wound.
Storage & Handling
Store lyophilized powder at -20C. LL-37 is susceptible to proteolytic degradation; reconstitute in sterile water and store at 2-8C for short-term use. Avoid repeated freeze-thaw cycles.
Frequently Asked Questions
What is LL-37?
LL-37 is the only human cathelicidin antimicrobial peptide — a 37-amino-acid peptide that serves as a key component of innate immune defense. It has direct antimicrobial, anti-biofilm, and wound healing properties.
How does LL-37 fight biofilms?
LL-37 disrupts bacterial biofilm formation at concentrations below its bactericidal threshold. This is significant because biofilms are a major cause of antibiotic-resistant chronic infections. The mechanism involves interference with bacterial quorum sensing and surface attachment.
Is LL-37 only antimicrobial?
No. Beyond direct microbial killing, LL-37 modulates immune cell recruitment, promotes wound healing via angiogenesis and re-epithelialization, and regulates inflammatory responses through Toll-like receptor signaling modulation.
Source LL-37 (Cathelicidin) for your research
98%+ purity, third-party tested, COA included