Important: LL-37 evidence is primarily from preclinical models. Limited human data exists for topical/local wound healing applications only. There is no human clinical trial evidence supporting systemic injectable use for immune modulation or infection treatment.
Overview
LL-37 is the only member of the cathelicidin family of antimicrobial peptides expressed in humans, derived from the C-terminal 37 amino acids of the hCAP18 precursor protein. It is produced by neutrophils, macrophages, epithelial cells, and NK cells as a critical component of the innate immune response, providing first-line defense against a broad spectrum of bacterial, viral, and fungal pathogens. Beyond its direct antimicrobial activity, LL-37 is a potent immunomodulatory molecule that bridges innate and adaptive immunity. It modulates toll-like receptor (TLR) signaling, promotes dendritic cell maturation, regulates neutrophil function, and stimulates angiogenesis and wound healing — making it one of the most multifunctional peptides in the human immune system.
Mechanism of Action
LL-37 exerts antimicrobial activity through membrane disruption: the cationic peptide is electrostatically attracted to the negatively charged lipopolysaccharide (LPS) of Gram-negative bacteria and the teichoic acids of Gram-positive bacteria. Upon membrane contact, LL-37 inserts its hydrophobic face into the lipid bilayer, forming pores or disrupting membrane integrity through a carpet or toroidal pore mechanism, leading to bacterial lysis. In its immunomodulatory role, LL-37 acts as a ligand for multiple receptors: it activates formyl peptide receptor-like 1 (FPRL1/FPR2) on neutrophils and monocytes, modulates TLR2, TLR4, and TLR9 signaling (both activating and inhibiting depending on con
Research Evidence
- Only human cathelicidin — broad-spectrum antimicrobial activity against bacteria, viruses, and fungi
- Membrane disruption mechanism: cationic amphipathic helix disrupts bacterial lipid bilayers
- Modulates TLR2, TLR4, TLR9 signaling — bridges innate and adaptive immunity
- LPS neutralization prevents TLR4-mediated endotoxin shock in preclinical models
- Promotes angiogenesis via VEGF-A upregulation and FPR2-mediated signaling
Bottom line: LL-37 is your body
Research Protocols & Dosage
Evidence-based research protocols, administration routes, and dosage considerations for LL-37 are detailed in the full compound profile. See also: Dosage guide for LL-37.
Sourcing & Quality
LL-37 is available from Purgo Labs with third-party COA verification and research-grade purity standards. View LL-37 at Purgo Labs.