LL-37

What is LL-37?

LL-37 is a 37-amino-acid antimicrobial peptide produced by cleavage of a larger precursor called hCAP-18. It belongs to the cathelicidin family and is one of the few human antimicrobial peptides of this family. The name derives from its first amino acids and its length.

It occurs in various tissues and body fluids, and its expression increases during infection or inflammation. This makes it a key player in innate immunity — the first line of defence, which responds quickly and non-specifically.

How does it work?

LL-37 is amphiphilic: it has a part that is attracted to water and a part that is attracted to fats. As a result, it can bind to bacterial membranes and damage them. Other mechanisms have also been described:

• modulation of inflammatory cytokines;
• effects on cells such as macrophages and neutrophils;
• participation in wound healing;
• interactions with DNA and other intracellular targets under certain circumstances.

Its broad spectrum of activity makes it interesting for research, but this breadth also makes effects and possible adverse reactions harder to predict.

Why is it relevant today?

Bacterial resistance to antibiotics is a major public health challenge. Antimicrobial peptides are therefore intensively studied: they act differently from classic medicines and could complement existing approaches. LL-37 is often used as a model peptide in these studies.

It is important to emphasise, however: research interest is not clinical approval. Peptides can be unstable, cytotoxic at higher concentrations or immunogenic. The path from the laboratory to a medicine is long and, for most candidates, unsuccessful.

Quality

LL-37 is sensitive to proteolysis and aggregation. Research must verify:

• purity by HPLC;
• identity by mass spectrometry;
• water and salt content;
• reconstitution and storage conditions.

The listing declares a purity of ≥ 98 % (HPLC). Verify the batch data and the COA with the source.

Safety and limitations

LL-37 is not an approved medicine. Data on systemic safety in humans are limited. Research use requires an appropriate laboratory environment, personal protective equipment and compliance with regulations.

Conclusion

LL-37 is an important model peptide of innate immunity and a promising target in antimicrobial research. Nevertheless, it remains a laboratory tool, not a medicine.