LL-37
The only human cathelicidin peptide: a 37-residue antimicrobial and immunomodulatory peptide expressed across barrier tissues.
Overview
LL-37 is the only cathelicidin-family antimicrobial peptide in humans, a 37-amino-acid cationic peptide cleaved from the C-terminus of the hCAP18 precursor protein. It is expressed by epithelial cells, keratinocytes, and immune cells and is found in many body fluids and barrier tissues. Beyond direct antimicrobial activity, LL-37 is recognized as a multifunctional host-defense peptide with immunomodulatory, chemotactic, and wound-healing activities, making it an active topic in infection and inflammation research.
Mechanism
LL-37 is amphipathic and cationic, properties that let it bind and disrupt bacterial membranes and neutralize lipopolysaccharide. It also modulates host responses through receptor-mediated signaling, chemoattraction of immune cells, promotion of angiogenesis, and regulation of epithelial cell migration and proliferation. Its expression is regulated by vitamin D signaling in many cell types, linking it to nutritional and innate-immune research.
Dosing
Research use is primarily in cell culture and animal models, where LL-37 is applied at concentrations or microgram doses specified per study, including topical and injected routes in wound and infection models. No approved human therapeutic dosing exists.
Expected Effects
- direct antimicrobial activity against bacteria and biofilms in vitro
- modulation of inflammatory cytokine responses in cell and animal models
- promotion of wound closure and angiogenesis in preclinical studies
- altered LL-37 levels implicated in skin diseases such as rosacea and psoriasis
Side Effects & Tolerability
Because LL-37 is pro-inflammatory at higher concentrations, its overexpression has been linked in the literature to inflammatory skin pathology, which argues for caution in dosing and a need for controlled safety studies. Systematic human safety data for exogenous administration are limited.
Storage
Lyophilized LL-37 should be stored desiccated, protected from light, and kept frozen at -20 deg C or below. Because it is prone to aggregation, reconstitution should follow the supplier guidance, and repeated freeze-thaw cycles should be avoided.