Host-defense

LL-37.

A natural human host-defense peptide with genuinely complex biology — and a double-edged role in inflammation.

Host-defenseInvestigationalSourced profile
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This is educational information, not medical advice, and The Peptide University does not sell peptides, supplies, or supplements. Many compounds discussed here are sold as “research chemicals” and are not approved for human use outside of clinical trials. Laws vary by country, and nothing here is a recommendation to obtain or use anything. Talk to a qualified clinician about your own situation.

● Investigational — not approved for human use

LL-37 is a naturally occurring human antimicrobial (host-defense) peptide, part of the cathelicidin family. Synthetic LL-37 is experimental, with no approved consumer use.

How it works

It has direct antimicrobial activity and also modulates immune responses and wound healing. Importantly, its effects are context-dependent — it can be protective or pro-inflammatory depending on setting.

The evidence

There's substantial basic-science interest and some clinical research (e.g., wound healing), but robust human evidence for the uses it's marketed for is limited. Its double-edged inflammatory role complicates simple “more is better” thinking.

Safety

Because it can drive inflammation and has been linked to certain inflammatory conditions in research, injecting synthetic LL-37 is not a well-characterized or clearly safe intervention. Human safety data is limited.

FAQ

QIsn't it 'natural,' so safe?

It's a natural peptide, but its biology is double-edged (pro- and anti-inflammatory), and injecting synthetic versions is unproven — natural doesn't mean safe.

QIs it approved?

No — experimental.

Sources

This profile summarizes the following. Follow the links to read the originals — and remember that summaries age, so check for newer information.

Inclusion here is not endorsement of any source's claims; several are cited so you can compare how different outlets characterize the same evidence.

Questions & comments

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