Mechanism of Action.
LL-37 is the only human cathelicidin antimicrobial peptide, cleaved from the precursor protein hCAP-18 by proteinase 3. As an amphipathic alpha-helical peptide, LL-37 disrupts microbial membranes through electrostatic interactions with negatively charged lipid bilayers, forming pores that kill bacteria, enveloped viruses, and fungi. Beyond direct antimicrobial activity, LL-37 has extensive immunomodulatory functions: it recruits immune cells through chemotactic activity (attracts neutrophils, monocytes, and T-cells), promotes wound healing by stimulating angiogenesis and re-epithelialization, modulates TLR signaling, neutralizes bacterial lipopolysaccharide (LPS), and promotes autophagy in macrophages. It also acts as an alarmin, bridging innate and adaptive immunity.
Research Summary.
LL-37 research spans antimicrobial defense, wound healing, and immune modulation. Studies demonstrate activity against MRSA, Pseudomonas aeruginosa, E. coli, Candida species, and enveloped viruses including influenza. In wound healing research, LL-37 promotes keratinocyte migration, angiogenesis, and tissue remodeling. Deficiency in LL-37 expression is associated with increased susceptibility to infections, particularly in burn patients and those with chronic wounds. Research has explored LL-37 for biofilm disruption, which is relevant to chronic infections resistant to conventional antibiotics. Its role in conditions like rosacea (where overexpression contributes to inflammation) has informed understanding of its dual nature as both protective and potentially inflammatory at high concentrations.
Side Effects & Safety.
LL-37 is an endogenous peptide, but exogenous administration carries specific considerations. At high concentrations, LL-37 can be cytotoxic to host cells through the same membrane-disruption mechanism that kills microbes. It may trigger mast cell degranulation and histamine release, potentially causing inflammatory reactions. Overexpression is associated with psoriasis and rosacea pathology, suggesting that excessive LL-37 can drive inflammation. Injection site reactions are possible. As a Category 2 peptide, it has additional regulatory considerations. Dosing must balance antimicrobial efficacy with host tissue tolerance.
Legal Status & Access.
LL-37 is classified as a Category 2 research peptide, reflecting its more potent biological activity profile and additional regulatory consideration. Available from select research peptide suppliers for laboratory investigation.