What Is LL-37?
LL-37 is the only member of the cathelicidin family of antimicrobial peptides in humans — a 37-amino-acid peptide cleaved from its precursor protein hCAP18 by the enzyme kallikrein. It is an amphipathic helical peptide produced by neutrophils, macrophages, mast cells, and epithelial cells at sites of infection and inflammation, representing a front-line innate immune defense factor.
Antimicrobial and Antibiofilm Mechanism
LL-37 kills bacteria, fungi, viruses, and parasites through direct membrane disruption — inserting into microbial membranes and forming pores that lyse the cell. Its broad-spectrum activity covers gram-positive bacteria (including MRSA), gram-negative bacteria, enveloped viruses, and fungi. Crucially, it is active against biofilm — the organized, drug-resistant matrix that allows bacteria to evade conventional antibiotics — making it particularly relevant for chronic wound infection research.
Wound Healing and Immunomodulation
Beyond antimicrobial activity, LL-37 promotes keratinocyte migration and proliferation (re-epithelialization), stimulates angiogenesis via VEGF receptor transactivation, and modulates macrophage activity to promote the M2 healing phenotype. It also attracts neutrophils and monocytes, stimulates mast cell degranulation, and directly activates dendritic cells — shaping both innate and adaptive immune responses to infection.
Quick Reference
Member reference tables summarize the compound's research parameters.
Research Indications
Research Protocols
As reported in cited literature and research-community logs (see Research Citations below), not a personal dosing recommendation.
This member section describes parameters reported in the research literature.
Peptide Interactions
This member section summarizes reported compound interactions and evidence limitations.
Reported Research Time Points
This member section summarizes reported research time points.
Safety Notes
Included for harm-reduction awareness only, in the event this compound is encountered outside its labeled research use. Inclusion here does not imply RUO Codes endorses, recommends, or instructs human use.
This member section discusses research safety considerations and uncertainties.
Quality Indicators
Research Citations
- Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial
Grönberg, A., Mahlapuu, M., Ståhle, M., Whately-Smith, C., Rollman, O., 2014, Wound Repair and Regeneration - LL-37, the master antimicrobial peptide, its multifaceted role from combating infections to cancer immunity
Keshri, A.K., Rawat, S.S., Chaudhary, A., Sharma, S., Kapoor, A., Mehra, P., Kaur, R., Mishra, A., Prasad, A., 2025, International Journal of Antimicrobial Agents - Structures of human host defense cathelicidin LL-37 and its smallest antimicrobial peptide KR-12 in lipid micelles
Wang, G., 2008, Journal of Biological Chemistry - Antimicrobial peptide LL-37 is bactericidal against Staphylococcus aureus biofilms
Noore, J., Noore, A., Li, B., 2019, PLOS ONE - The Potential of Human Peptide LL-37 as an Antimicrobial and Anti-Biofilm Agent
Ridyard, K.E., Overhage, J., 2021, Antibiotics - Discovery of novel antibacterial agent for the infected wound treatment: all-hydrocarbon stapling optimization of LL-37
Zhang, Y., Zheng, M., Wang, Z., Liu, Z., Chen, S., Li, X., Shi, Y., Hu, H., 2024, Theranostics - LL-37: Structures, Antimicrobial Activity, and Influence on Amyloid-Related Diseases
Bhattacharjya, S., Zhang, Z., Ramamoorthy, A., 2024, Biomolecules - Alanine and lysine scans of the LL-37-derived peptide fragment KR-12 reveal key residues for antimicrobial activity
Gunasekera, S., Muhammad, T., Strömstedt, A.A., Rosengren, K.J., Göransson, U., 2018, ChemBioChem - Renovation as innovation: Repurposing human antibacterial peptide LL-37 for cancer therapy
Liu, R., Xu, Y., Chen, M., Weïwer, M., Zhou, X., Bridges, A.A., DeJesus, M.A., Kelley, L., Negami, T., Vo, N.N., et al., 2021, Pharmacological Research - LL-37-derived short antimicrobial peptide KR-12-a5 and its d-amino acid substituted analogs with cell selectivity, anti-biofilm activity, synergistic effect with conventional antibiotics, and anti-inflammatory activity
Kim, E.Y., Rajasekaran, G., Shin, S.Y., 2017, European Journal of Medicinal Chemistry - LL-37, a Multi-Faceted Amphipathic Peptide Involved in NETosis
Radic M, Muller S, 2022, Cells - Cathelicidin peptide LL-37: A multifunctional peptide involved in heart disease
Miao S, Liu H, Yang Q, 2024, Pharmacol Res - Human cathelicidin peptide LL-37 induces endothelial-to-mesenchymal transition
Suzuki K, Ohkuma M, Nagaoka I, 2025, Biosci Biotechnol Biochem - Human host-defense peptide LL-37 targets stealth siderophores
Zsila F, Beke-Somfai T, 2020, Biochem Biophys Res Commun - Human Cathelicidin Peptide LL-37 Induces Cell Death in Autophagy-Dysfunctional Endothelial Cells
Suzuki K, Ohkuma M, Someya A, 2022, J Immunol