LL-37
Also known as: Cathelicidin, Human antimicrobial peptide 18, hCAP18
The only member of the cathelicidin family of host defense peptides in humans. Has broad-spectrum antimicrobial activity and diverse immunomodulatory effects.
Overview
LL-37 is the C-terminal bioactive fragment of the precursor protein hCAP18 (human cathelicidin antimicrobial protein 18). It is produced by neutrophils, macrophages, mast cells, and epithelial cells as part of innate immune defense. LL-37 exhibits direct antimicrobial activity against a broad range of bacteria, fungi, and some viruses by disrupting microbial membranes, while simultaneously modulating host immune responses.
Beyond antimicrobial defense, LL-37 binds to formyl peptide receptor-like 1 (FPRL-1/FPR2) to modulate inflammation, wound healing, and angiogenesis. Its roles in cancer biology are complex — promoting angiogenesis in some tumors while inducing apoptosis in others. Research has also explored its involvement in autoimmune conditions (LL-37 can form complexes with DNA that activate plasmacytoid dendritic cells in SLE), making it a target of interest in both infection and autoimmunity.
Mechanism of Action
LL-37 kills bacteria by electrostatic interaction with negatively charged microbial membranes, forming pores that disrupt membrane integrity. In host cells, it activates FPR2/FPRL-1, triggering calcium mobilization and ERK1/2 signaling. It induces chemokine production to recruit adaptive immune cells and promotes wound healing through EGFR transactivation and VEGF upregulation.
Research Areas
- ●Broad-spectrum antimicrobial activity
- ●Wound healing and angiogenesis
- ●Innate immune modulation
- ●Lupus and autoimmune pathogenesis
- ●Lung defense (cystic fibrosis, pneumonia models)
- ●Antiviral research (influenza, HIV, SARS-CoV-2)
- ●Cancer biology (pro- and anti-tumor effects)
Storage & Handling
Lyophilized: -20°C. Reconstituted: 2–8°C, 14 days. Avoid freeze-thaw cycles.
Soluble in sterile water; can aggregate at high concentrations
For Research Use Only. This information is provided for educational and research purposes. LL-37 is not approved for human consumption, veterinary use, or clinical application. All research must be conducted in accordance with applicable laws and institutional guidelines.