LL-37

LL-37 (leucine-leucine-37) is the C-terminal 37-amino acid peptide cleaved from human cathelicidin (hCAP18). It is the only cathelicidin peptide found in humans and serves as a first-line innate immune defense molecule.

LL-37 exerts direct antimicrobial activity against bacteria, viruses, and fungi by disrupting microbial membranes. But its role extends far beyond direct killing: it modulates immune cell recruitment, promotes wound healing, influences adaptive immunity, and can neutralize bacterial endotoxins (LPS).

Research has shown that individuals with low LL-37 levels are more susceptible to infections, while appropriate levels support robust immune surveillance. LL-37 also promotes angiogenesis and tissue repair at wound sites, making it a dual-function immune and healing peptide.

Deficiencies in LL-37 have been associated with increased susceptibility to respiratory infections, urinary tract infections, and chronic wound healing impairment.