LL-37

What Is LL-37?

LL-37 is a peptide produced by immune cells and the cells lining organs like the skin and gut, released as part of the body's innate immune response, the first, fast-acting layer of defense against infection. It's derived from a larger precursor protein and gets its name from starting with two leucine amino acids, abbreviated "LL," followed by a chain of 37 amino acids total.

It's the only cathelicidin peptide found in humans, a family of antimicrobial peptides present across many mammals. Beyond its role fighting pathogens directly, researchers have found LL-37 involved in a second, seemingly unrelated process: helping skin wounds close and heal.

What LL-37 Is Being Researched For

• Antimicrobial Defense

  The foundational area of LL-37 research is its ability to directly kill or disable a broad range of bacteria, fungi, and viruses as part of the body's innate immune response.

• Wound Healing

  Research has found LL-37 plays a distinct role in skin wound closure, showing up at high levels in healing skin and appearing to support the movement and growth of the cells that reseal a wound.^[1]

• Blood Vessel Formation

  Beyond wound closure specifically, LL-37 has been studied for its ability to promote the formation of new blood vessels, a related process that supports tissue repair.^[2]

How LL-37 Works

• Disrupting Bacterial Membranes

  Research points to LL-37's antimicrobial action coming from its positive electrical charge, which allows it to bind to and disrupt the negatively charged outer membranes of bacteria, creating pores that compromise the microbe's structure.

• Supporting Wound Closure

  Research points to LL-37 being produced by skin cells specifically during the healing process, with studies finding that blocking LL-37 with antibodies slowed the movement of new skin cells across a wound. This suggests LL-37 plays an active role in re-epithelialization, the process of skin cells migrating to close a wound.^[1]

• Promoting New Blood Vessel Growth

  Research points to LL-37 stimulating the formation of new blood vessels by increasing the activity of a signaling protein involved in blood vessel growth, a mechanism separate from its antimicrobial action that supports the broader tissue repair process.^[2]

Reconstitution and Handling

LL-37 is typically supplied as a lyophilized powder in a sealed vial and reconstituted with bacteriostatic water before use in a research setting. Water should be added slowly rather than injected directly into the powder, and the vial should be swirled, not shaken.

Since the amount of water used affects the concentration of the final solution, researchers often use a dosage calculator to work this out before mixing. Once reconstituted, the solution is kept refrigerated to help preserve its stability.

Key Takeaways

LL-37 stands out for playing two distinct roles in the body's defense and repair systems: directly disrupting microbes as part of innate immunity, and separately supporting the cell movement and blood vessel growth involved in wound healing. Its research base spans both of these areas, with reduced LL-37 levels specifically linked to chronic, non-healing wounds. As the only cathelicidin peptide in humans, it remains a heavily studied molecule at the intersection of infection defense and tissue repair.

Frequently Asked Questions

Sources and Research

1. Heilborn JD, Nilsson MF, Kratz G, Weber G, Sørensen O, Borregaard N, Ståhle-Bäckdahl M. The cathelicidin anti-microbial peptide LL-37 is involved in re-epithelialization of human skin wounds and is lacking in chronic ulcer epithelium. J Invest Dermatol. 2003;120(3):379-389.
2. Koczulla R, von Degenfeld G, Kupatt C, et al. An angiogenic role for the human peptide antibiotic LL-37/hCAP-18. J Clin Invest. 2003;111(11):1665-1672.