LL-37
Research Overview · Mechanism of Action · Reconstitution Guide
Overview
LL-37 is the only known human cathelicidin antimicrobial peptide, derived from the C-terminal region of the 18 kDa human cationic antimicrobial protein (hCAP18). It is a 37-amino acid amphipathic alpha-helical peptide expressed in neutrophils, epithelial cells, and macrophages. LL-37 is a multifunctional innate immunity effector with direct antimicrobial activity, immunomodulatory properties, wound healing promotion, and angiogenic effects. Its expression is induced by vitamin D3 and various microbial stimuli.
Mechanism of Action
LL-37 disrupts bacterial membranes through electrostatic interaction with anionic lipopolysaccharide (LPS) and phospholipid bilayers, forming pores that cause osmotic lysis. Beyond direct antimicrobial activity, LL-37 acts as a chemokine, recruiting neutrophils, monocytes, and T-cells via formyl peptide receptor-like 1 (FPRL1). It neutralizes LPS-induced TLR4 signaling, modulating septic inflammatory responses. LL-37 also promotes keratinocyte migration and proliferation, angiogenesis via VEGF-A upregulation, and has been studied for its role in autoimmune conditions including psoriasis and lupus.
Key Studies & References
Zanetti M (2004). Cathelicidins, multifunctional peptides of the innate immunity. J Leukoc Biol 75:39–48.
Nijnik A & Hancock RE (2009). Host defence peptides: antimicrobial and immunomodulatory activity and potential applications for tackling antibiotic-resistant infections. Curr Opin Hematol 16:41–47.
Heilborn JD et al. (2003). The cathelicidin anti-microbial peptide LL-37 is involved in re-epithelialization of human skin wounds and is lacking in chronic ulcer epithelium. J Invest Dermatol 120:379–389.
Bacteriostatic Water Reconstitution Guide
Research Use Only — The following reconstitution information is provided for in vitro laboratory research purposes only. Not for human or veterinary use.
Recommended Solvent
Bacteriostatic water (0.9% benzyl alcohol) or sterile saline
Standard Volume
Add 1 mL bacteriostatic water to a 5 mg vial to yield a 5000 mcg/mL (5 mg/mL) solution.
Working Concentration
5 mg/mL standard. Dilute to working concentration as needed.
Storage (Reconstituted)
Reconstituted: 2–8°C, use within 14 days. Lyophilized: -20°C, desiccated.
Stability Window
LL-37 is prone to aggregation and adsorption to surfaces. Use within 14 days of reconstitution. Low-binding tubes are recommended for research use.
Technique
Inject solvent slowly. Swirl gently. LL-37 has a tendency to aggregate — ensure complete dissolution before use. Solution should be clear.
Notes
LL-37's amphipathic helical structure makes it prone to self-aggregation, especially at higher concentrations. Dilute to working concentration immediately before use. Avoid repeated freeze-thaw of reconstituted solution.
Research Dosing Reference
The following dosing information is derived from published preclinical research literature and is provided for reference purposes only.
Clinical / Human Research Range
Topical wound healing studies: 0.5–2 mg/mL formulations. Systemic research: limited human data.
Preclinical Models
Rodent wound models: 10–100 mcg topical or subcutaneous. In vitro: 1–10 mcg/mL for antimicrobial and immunomodulatory assays.
Calculation Example
For a 5 mg/mL solution: a 1 mg research dose = 0.2 mL. Dilute to 1 mg/mL (1:5) for in vitro work: 0.1 mL stock + 0.4 mL buffer.