LL-37

What is LL-37?

LL-37 occupies a unique position in human immunology: it is the only antimicrobial peptide produced by the human cathelicidin family, unlike other species that express multiple cathelicidin variants. Cleaved from the C-terminus of the hCAP18 precursor protein, this amphipathic alpha-helical peptide demonstrates broad-spectrum antimicrobial activity against bacteria, fungi, and enveloped viruses through membrane disruption. Beyond direct antimicrobial action, LL-37 exhibits immunomodulatory functions—recruiting immune cells, modulating inflammatory responses, and promoting wound closure.

Expression of LL-37 is induced by vitamin D, linking nutritional status to innate immune capacity—a relationship that has made this peptide central to research on vitamin D-dependent immunity. Its multi-functional profile (antimicrobial, chemotactic, angiogenic, and wound-healing) makes LL-37 essential for studying the complex roles of antimicrobial peptides beyond simple pathogen killing.

Mechanism of Action

LL-37 exerts antimicrobial activity through multiple complementary mechanisms. As an amphipathic α-helical peptide, it inserts into bacterial membranes, disrupting lipid bilayer integrity and causing membrane depolarization and cell lysis. The peptide's cationic residues enable electrostatic interaction with negatively charged bacterial membrane components (lipopolysaccharide, lipoteichoic acid), while its hydrophobic face facilitates membrane insertion. This dual nature allows LL-37 to discriminate between bacterial and mammalian membranes based on charge distribution differences.

Beyond direct antimicrobial effects, LL-37 functions as an immunomodulator by binding formyl peptide receptor-like 1 (FPRL1) and purinergic P2X7 receptors on immune cells. This receptor engagement triggers chemotaxis, modulates cytokine production, and enhances phagocytosis. LL-37 also neutralizes bacterial endotoxins, suppresses inflammatory cascades initiated by pattern recognition receptors, and promotes wound healing through effects on keratinocyte migration and angiogenesis—making it a multifunctional innate immune effector.

Key Research Findings

• Demonstrated broad-spectrum antimicrobial activity through direct membrane disruption and immunomodulatory effects on multiple immune cell populations (Vandamme et al. Cell Immunol 2012;280(1):22-35. PMID: 23246832)
• Modulates inflammatory responses by neutralizing bacterial endotoxins and regulating cytokine production through interaction with formyl peptide receptors
• Promotes wound healing and tissue repair through chemotactic effects on keratinocytes and endothelial cells, supporting angiogenesis and re-epithelialization

Research Applications

• Antimicrobial mechanism studies
• Innate immunity research
• Membrane disruption models
• Biofilm penetration research
• Immune cell chemotaxis
• Wound healing immunity
• Vitamin D-dependent peptide regulation

Reconstitution & Use

Reconstitute with bacteriostatic water for laboratory use. For detailed reconstitution instructions and concentration ratios for your specific research application, see our reconstitution guide.

Storage & Handling

Store lyophilized at -20°C. Upon reconstitution, maintain at 2-8°C and use within 30 days. The amphipathic structure requires gentle handling to prevent aggregation at higher concentrations.