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Immunology · LL-37

LL-37: the human cathelicidin and biofilm research

October 6, 2026 · 1 min read · Models: Cell culture, Bacterial culture

LL-37 is the only human cathelicidin antimicrobial peptide. Beyond killing bacteria by disrupting membranes, it modulates immune signaling and, at sub-lethal concentrations, prevents biofilm formation by Pseudomonas aeruginosa in vitro.

A summary of published research for scientific reference. It is not medical advice and does not describe or endorse use in humans or animals. Findings from cell culture and animal models often do not carry over to other systems.

Structure and processing

LL-37 is a 37-residue amphipathic α-helical peptide, named for its two N-terminal leucines. It is cleaved from the precursor hCAP18 by proteases such as proteinase 3 and kallikreins. Neutrophils, epithelial cells and keratinocytes produce it, and vitamin D signaling regulates its expression.

Antimicrobial and antibiofilm activity

Like many cationic host-defence peptides, LL-37 binds negatively charged bacterial membranes and disrupts them. Overhage and colleagues (Infection and Immunity, 2008) found that it inhibits P. aeruginosa biofilm formation at concentrations well below those needed to kill the bacteria. It did this by changing attachment, twitching motility and quorum-sensing gene expression.

Immunomodulation

LL-37 also acts as a signaling molecule. It binds self-DNA and self-RNA and can activate plasmacytoid dendritic cells, it modulates TLR responses, and it chemoattracts immune cells via formyl-peptide receptor-like 1. These dual roles make it a model system for studying how antimicrobial peptides affect host cells.

Considerations for in-vitro work

Activity is strongly affected by salt concentration, serum proteins and proteolysis. Many published MIC values were measured in low-salt media, so test conditions should be reported carefully.

References

  1. Dürr UHN, Sudheendra US, Ramamoorthy A. LL-37, the only human member of the cathelicidin family of antimicrobial peptides. Biochim Biophys Acta. 2006;1758(9):1408–1425.
  2. Overhage J, Campisano A, Bains M, et al. Human host defense peptide LL-37 prevents bacterial biofilm formation. Infect Immun. 2008;76(9):4176–4182.