What it is
LL-37 is a peptide made of 37 amino acids. The human body makes it naturally, and it can also be made in a lab. It is the only cathelicidin humans make. Cathelicidins are a family of peptides that kill germs. The body cuts LL-37 from a larger protein called hCAP18. White blood cells and the cells that line the skin, lungs, and gut release it. The name comes from its first two amino acids, both leucine (L), and its length of 37. Vitamin D turns on the gene that makes it. Other names: Cathelicidin, hCAP18, CAP-18.
What researchers study it for
- Killing bacteria, fungi, and viruses in lab tests
- Signals between immune cells
- Skin cell movement and wound closing
- Skin diseases like rosacea, eczema, and psoriasis
- Blood vessel growth
What the studies found
1. It kills germs by breaking open their outer layer.
This 2006 review describes how LL-37 works. LL-37 has a positive charge. Bacterial membranes have a negative charge, so LL-37 is pulled onto them. It then makes holes in the membrane, and the cell breaks open. Lab tests show it works against bacteria, fungi, and some viruses.
2. It changed how dendritic cells develop.
Dendritic cells show pieces of germs to T cells. T cells then decide what kind of immune response to mount. In this 2004 study, LL-37 changed the dendritic cells' surface markers and the signals they released. It also changed the type of T cell response they triggered. Lab cells only. This shows LL-37 affects immune signaling, not only germ killing.
3. Human skin cells closed a scratch faster.
A 2005 study made a scratch across a layer of human skin cells in a dish. LL-37 made the cells move in and close the gap faster. It worked by turning on the epidermal growth factor receptor, a receptor that tells skin cells to grow and move. When that receptor was blocked, the effect stopped. Lab cells only.
How much research exists
It is well studied as a natural part of the immune system. There are many lab cell and animal studies. As a treatment, it is still at an early stage. No LL-37 product is approved.
Facts
- Formula: C205H340N60O53
- Weight: 4493.3 g/mol
- CAS number: 154947-66-7
- Sequence: LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
- Time in the blood: not measured. Enzymes break it down quickly.
- Storage: freeze the dry powder. Keep mixed solution in the fridge.
Legal status
Not approved by the FDA or any other agency for human use. Banned in sports by WADA under section S0, which covers drugs not approved for human use.
For research use only. Not for human use. Nothing here is medical advice.