What is the difference between LL-37 and Thymosin Beta-4 Fragment (TB4-Frag 17-23)?

LL-37: LL-37 is the only human cathelicidin — a host defense peptide produced by neutrophils, epithelial cells, and macrophages in response to infection and inflammation. It functions simultaneously as a broad-spectrum antimicrobial agent and an immune-modulatory signaling molecule. Research interest has expanded dramatically since COVID-19 studies linked low LL-37 levels to severe outcomes, and gut health research identified it as a key regulator of intestinal barrier integrity. Thymosin Beta-4 Fragment (TB4-Frag 17-23): The heptapeptide fragment (amino acids 17–23) of full thymosin beta-4, sequence Ac-LKKTETQ. This sequence is the active actin-binding domain responsible for TB-500's tissue repair properties. Shorter molecular weight than TB-500 enables more targeted delivery while retaining identical mechanism of action on G-actin regulation and tissue repair signaling. Both are in the Healing & Recovery category but differ in mechanism, dosing, and research evidence — see the full comparison.

Can you take LL-37 and Thymosin Beta-4 Fragment (TB4-Frag 17-23) together?

There is no specific, well-documented interaction rule for combining LL-37 and Thymosin Beta-4 Fragment (TB4-Frag 17-23) in the aggregated research reviewed. Combining peptides should only be considered under professional supervision. This is not medical advice.

Which is better researched, LL-37 or Thymosin Beta-4 Fragment (TB4-Frag 17-23)?

LL-37 is currently research-stage and Thymosin Beta-4 Fragment (TB4-Frag 17-23) is research-stage. "Better researched" depends on your research goal — review each profile's cited sources.

Healing & Recovery · Comparison

LL-37 vs Thymosin Beta-4 Fragment (TB4-Frag 17-23)

A neutral, side-by-side comparison of two healing & recovery peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.

LL-37

Research-stage

LL-37 is the only human cathelicidin — a host defense peptide produced by neutrophils, epithelial cells, and macrophages in response to infection and inflammation. It functions simultaneously as a broad-spectrum antimicrobial agent and an immune-modulatory signaling molecule. Research interest has expanded dramatically since COVID-19 studies linked low LL-37 levels to severe outcomes, and gut health research identified it as a key regulator of intestinal barrier integrity.

Full profile

Thymosin Beta-4 Fragment (TB4-Frag 17-23)

Research-stage

The heptapeptide fragment (amino acids 17–23) of full thymosin beta-4, sequence Ac-LKKTETQ. This sequence is the active actin-binding domain responsible for TB-500's tissue repair properties. Shorter molecular weight than TB-500 enables more targeted delivery while retaining identical mechanism of action on G-actin regulation and tissue repair signaling.

Full profile

	LL-37	Thymosin Beta-4 Fragment (TB4-Frag 17-23)
Category	Healing & Recovery	Healing & Recovery
Also known as	Cathelicidin LL-37, hCAP-18 C-terminal fragment, CRAMP (murine equivalent)	TB4 fragment 17-23, TB-500 active peptide, LKKTETQ, thymosin beta-4 fragment, Ac-LKKTETQ
Evidence	Research-stage	Research-stage
Dosing range	100mcg–500mcg mcg, Daily or 3–5x weekly	250mcg–1mg mcg–mg, 2–3x weekly
Administration	Subcutaneous injection, Intranasal (for respiratory applications), Topical (wound care)	Subcutaneous injection, Intramuscular injection
Key side effects	Injection site redness and irritation (common — pro-inflammatory at injection site), Transient flu-like symptoms (immune activation), Local induration, High doses may be cytotoxic — dose-response curve is non-linear	Injection site irritation, Mild fatigue (transient), Potential headache, Generally well-tolerated in research applications
Cited sources	3 references	2 references

Key differences

Administration: LL-37 — Subcutaneous injection, Intranasal (for respiratory applications), Topical (wound care); Thymosin Beta-4 Fragment (TB4-Frag 17-23) — Subcutaneous injection, Intramuscular injection.
Dosing units differ: LL-37 is dosed in mcg, Thymosin Beta-4 Fragment (TB4-Frag 17-23) in mcg–mg — they operate at different scales.
Frequency: LL-37 is typically Daily or 3–5x weekly; Thymosin Beta-4 Fragment (TB4-Frag 17-23) is 2–3x weekly.
Research depth: this profile cites 3 sources for LL-37 vs 2 for Thymosin Beta-4 Fragment (TB4-Frag 17-23).

How each works

LL-37

LL-37 exerts antimicrobial activity by disrupting bacterial membranes via electrostatic interaction with negatively charged lipopolysaccharide — effective against gram-positive and gram-negative bacteria, fungi, and enveloped viruses including SARS-CoV-2 in vitro. Beyond direct antimicrobial action, LL-37 modulates innate immunity through TLR4 signaling, promotes wound healing via EGFR and FPRL1 receptor activation, and has demonstrated anti-biofilm activity against P. aeruginosa and S. aureus. Vitamin D is the primary driver of endogenous LL-37 production.

Thymosin Beta-4 Fragment (TB4-Frag 17-23)

The LKKTETQ sequence was identified in 1994 as the minimum active fragment of thymosin beta-4 responsible for its actin-sequestering and tissue repair activity. This heptapeptide competes with actin monomer binding proteins, promoting cell migration, angiogenesis, and wound healing. Studies confirm it recapitulates the key bioactivity of full TB4 in cell migration and collagen deposition assays.

Read the full LL-37 profile Read the full Thymosin Beta-4 Fragment (TB4-Frag 17-23) profile

This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.