LL-37 and the Dual Nature of Antimicrobial Peptide Signaling

An endogenous component of innate immunity

LL-37 is the active human cathelicidin peptide produced from hCAP18. It is expressed by epithelial and immune cells and participates in barrier defense, chemotaxis, inflammatory signaling, and responses to infection.

Membrane activity is not automatically selective

Cationic and amphipathic features let LL-37 interact with microbial membranes. The same behavior can affect host cells, especially at higher concentrations or in different ionic environments. Antimicrobial potency must be interpreted alongside hemolysis and cytotoxicity.

It is also an immune signaling molecule

LL-37 can bind nucleic acids and interact with several receptors and pathways. Depending on context, it may recruit immune cells, alter cytokine production, promote repair signals, or amplify inflammation.

Experimental conditions change the result

Salt, serum proteins, membrane composition, peptide aggregation, and assay format can substantially alter observed activity. A favorable result in a simplified microbial assay may not translate to complex tissue.

This article is provided for scientific and educational purposes. It does not describe or recommend human or veterinary use. Research findings may be limited by study design, model selection, material identity, sample size, or lack of independent replication.