LL-37

LL-37 is a 37-amino acid cationic amphipathic peptide — the only human cathelicidin — derived from the C-terminal region of the protein hCAP-18. It is produced primarily by neutrophils, macrophages, and epithelial cells as part of the innate immune response, making it a central component of the body's antimicrobial defense.

LL-37 has been studied extensively for its antimicrobial properties against gram-positive and gram-negative bacteria, fungi, enveloped viruses, and parasites. Its mechanism involves disruption of microbial membranes via electrostatic interaction with negatively charged phospholipids — a physical disruption mechanism that makes resistance development considerably harder than with conventional antibiotics. Research interest has intensified in the context of multidrug-resistant organisms.

Beyond antimicrobial activity, LL-37 modulates inflammation, acts as a chemoattractant, promotes angiogenesis, and has demonstrated wound healing activity in vitro and in vivo. Research has also examined its role in cancer biology, where context-dependent effects on tumor progression have been observed. This multifunctional profile makes LL-37 a compound of broad interest across infectious disease, immunology, and regenerative medicine research.