Description
LL-37 is the only human cathelicidin and the primary antimicrobial peptide of innate immunity in humans. Structurally it is a 37-amino-acid peptide released from the precursor protein hCAP-18 after proteolytic cleavage. The name “LL-37” derives from the two N-terminal leucine residues and the total length of 37 amino acids.
The research mechanism is multilayered. The central activity lies in direct antimicrobial action against bacteria, viruses and fungi. The cationic, amphipathic structure of LL-37 allows interaction with negatively charged microbial membranes and leads to membrane permeabilization. In preclinical studies, this broad antimicrobial spectrum has been documented.
Beyond direct antimicrobial activity, LL-37 shows immune-modulatory effects in research models: leukocyte chemotaxis, modulation of cytokine production, promotion of wound healing and angiogenic properties. This multi-modality makes LL-37 a mechanistically complex but well-characterized research tool at the interface between innate immunity and repair.
In preclinical studies, LL-37 has been used in wound healing models, skin research setups and inflammation studies. A particularity: LL-37 levels are altered in some chronic inflammation states, also making the compound relevant in pathophysiological research.
LL-37 is available in 5mg vials as 10-vial packs.
This information is for research and educational purposes only. No medical recommendations.
Risks & Safety
LL-37 is described as largely well tolerated per study reports. As an endogenous antimicrobial peptide of innate immunity, the compound is mechanistically well characterized.
Observed in research and user reports:
- Injection site: mild redness or irritation at the injection site is the most common local observation, typical for subcutaneously applied peptides.
- Membrane activity: the cationic, amphipathic structure of LL-37 permeabilizes microbial membranes. Local irritation is plausible as an expression of this activity.
- Immune modulation: beyond its antimicrobial action, LL-37 modulates chemotaxis and cytokine production, an active intervention in innate immunity. Altered LL-37 levels are documented in some chronic inflammation states.
- No long-term data: the characterization comes predominantly from preclinical models. Robust long-term human data do not exist.
This classification does not replace medical advice. Risk and responsibility for any actual use lie entirely with the buyer.
Studies
- LL-37, the only human member of the cathelicidin family of antimicrobial peptides - Biochimica et Biophysica Acta - Biomembranes 2006: Review of structure and biophysics: LL-37 is the only human cathelicidin-derived peptide, an amphipathic helical peptide of 37 residues with a broad antimicrobial spectrum, expressed in epithelia and leukocytes.
- The cathelicidin anti-microbial peptide LL-37 is involved in re-epithelialization of human skin wounds and is lacking in chronic ulcer epithelium - Journal of Investigative Dermatology 2003: After skin injury the precursor hCAP18 rises strongly in wound epithelium. It is absent at the edge of chronic ulcers. Antibodies against LL-37 inhibited re-epithelialization in an ex vivo model.
- An angiogenic role for the human peptide antibiotic LL-37/hCAP-18 - Journal of Clinical Investigation 2003: LL-37 activated endothelial cells via the receptor FPRL1 and induced angiogenesis, including in a rabbit hind-limb ischemia model. Mice lacking the corresponding cathelicidin showed reduced wound vascularization.
- Human host defense peptide LL-37 prevents bacterial biofilm formation - Infection and Immunity 2008: LL-37 inhibited Pseudomonas aeruginosa biofilm formation in vitro at just 0.5 µg/ml, far below the growth-inhibiting concentration of 64 µg/ml.
- Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trial - Wound Repair and Regeneration 2021: Phase 2b trial in 148 participants with chronic venous leg ulcers: topical LL-37 showed no significant benefit over placebo in the full study population. Only a post hoc analysis of large wounds suggested an effect.
