Host Defense Peptide / Cathelicidin Class / Innate Immunity Research Compounds
Antimicrobial Peptides Research — LL-37, Cathelicidins & Defensins
As of 2026-08-23, DMV Research documents Antimicrobial Peptides — LL-37 & Defensin Research Hub (HPLC purity ≥99%) across 4 research FAQs on this page, for laboratory research use only.
Antimicrobial peptides (AMPs) are short, amphipathic peptides that form a critical component of innate immunity across virtually all multicellular organisms. In humans, the primary cathelicidin is LL-37 — the mature C-terminal domain of the hCAP-18 precursor protein (CAS 154947-66-7; 37 residues; MW ~4493 Da; sequence: LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES). LL-37 is the most studied human AMP and serves as the archetype for the broader class. Alongside cathelicidins, the defensin family (α-defensins, β-defensins) constitutes the other major class of human AMPs, with roles in epithelial barrier defense, neutrophil granule function, and mucosal immunity. This hub covers LL-37 and the broader antimicrobial peptide research context. Research use only.
For laboratory research use only. Not for human or veterinary use. Not for diagnostic or therapeutic use. Not a drug, food, cosmetic, or dietary supplement.
Compound identity
- Name
- Antimicrobial Peptides — LL-37 & Defensin Research Hub
- Class
- Host Defense Peptide / Cathelicidin Class / Innate Immunity Research Compounds
- Also known as
- antimicrobial peptide research, LL-37 research, cathelicidin peptide, CAP-18 antimicrobial, host defense peptide research, defensin peptide research, innate immunity peptide, cathelicidin LL-37, antimicrobial host defense peptide, LL37 research compound, AMP research, cathelicidin antimicrobial peptide
Research context
LL-37's mechanism of action in antimicrobial models is primarily membrane disruption: the helical peptide inserts into bacterial membranes, forming pores or causing membrane disintegration through carpet-mechanism or toroidal-pore models. This broad-spectrum activity — effective against gram-positive and gram-negative bacteria, some fungi, and enveloped viruses — is of significant interest to researchers studying alternatives to conventional antibiotics, particularly against biofilm-forming pathogens and antibiotic-resistant organisms. In-vitro studies have examined LL-37's minimum inhibitory concentrations (MICs) against clinical isolates of S. aureus (including MRSA), P. aeruginosa (high biofilm producer), E. coli, and C. albicans. Anti-biofilm models are a particularly active area: LL-37 has been shown in vitro to disrupt P. aeruginosa biofilm formation at sub-MIC concentrations.
Beyond direct antimicrobial activity, LL-37 is studied as an immunomodulator. It is expressed by neutrophils, macrophages, NK cells, and epithelial cells and is upregulated in response to infection, inflammation, and vitamin D signaling — the vitamin D receptor (VDR) directly regulates cathelicidin gene expression, which underlies research interest in the LL-37/vitamin D axis. Immunomodulatory research contexts include: macrophage activation, chemotaxis of immune cells (LL-37 acts as a chemoattractant for monocytes and T cells), mast cell degranulation, and wound healing models. The peptide also interacts with TLR3 and TLR9, modulating innate immune signaling through non-antimicrobial pathways. These diverse effects make LL-37 one of the most multifunctional research peptides available.
For researchers sourcing antimicrobial peptides: LL-37's 37-residue length places it at the upper end of research peptide synthesis complexity; purity by HPLC (≥98%+) and endotoxin testing are particularly important for antimicrobial peptide research because LPS contamination confounds innate immunity readouts. Defensins (α-defensins HNP-1–4 from neutrophils; β-defensins hBD-1–3 from epithelia) are studied in this context and are synthesized with disulfide bonds requiring oxidative folding — technically distinct from LL-37. LL-37 is typically offered as a synthetic research peptide with ≥99% purity, HPLC data, and mass-spec COA. Research use only.
Related research
Antimicrobial Peptides — LL-37 & Defensin Research Hub is profiled alongside DMV Research's other host defense peptide overviews, including Thymosin Alpha-1, Thymosin Beta-4, KPV, LL-37, and Thymalin — Thymus Peptide Bioregulator (Khavinson Research) — each with its own identity data, cited literature, and FAQ. See the Antimicrobial Peptides — LL-37 & Defensin Research Hub Certificate of Analysis for lab-verified purity data.
Frequently asked questions
What is LL-37 and why is it studied?+
LL-37 (CAS 154947-66-7, 37 residues, MW ~4493 Da) is the mature C-terminal domain of the human cathelicidin precursor protein hCAP-18 — the only cathelicidin expressed in humans. It is studied for broad-spectrum antimicrobial activity (gram-positive, gram-negative, fungi, enveloped viruses), anti-biofilm effects, and immunomodulatory functions including macrophage activation, chemotaxis, and wound healing models. Research use only.
What is the sequence and structure of LL-37?+
LL-37 sequence (N→C): LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES (37 residues). It adopts an amphipathic α-helical conformation in lipid environments, which underlies its membrane-disruption mechanism. CAS: 154947-66-7; MW: ~4493 Da; no disulfide bonds (unlike defensins). Research use only.
How does LL-37 differ from defensins as antimicrobial peptides?+
LL-37 is a cathelicidin — a single-peptide, α-helical AMP with broad-spectrum activity and no disulfide bonds. Defensins (α-defensins from neutrophil granules; β-defensins from epithelial cells) are β-sheet structures stabilized by 3 disulfide bonds, require oxidative folding in synthesis, and have distinct receptor interactions and expression patterns. Both classes are host defense peptides from human innate immunity; LL-37 is the better-studied research compound. Research use only.
What research applications use LL-37?+
Key research applications: (1) antimicrobial MIC assays against gram-positive/negative organisms and MRSA; (2) anti-biofilm models (P. aeruginosa, S. aureus); (3) innate immunity signaling (TLR3/9 modulation, macrophage activation); (4) wound healing and epithelial repair models; (5) vitamin D/cathelicidin axis studies. All are in-vitro or animal-model research; LL-37 has no regulatory approval as a therapeutic agent. Research use only.
Research use only
All products are intended for laboratory and research use only (RUO) and are not for human consumption, ingestion, or any in-vivo use.
The statements on this page have not been evaluated by the FDA. For laboratory research use only. Not for human or veterinary use. Not for diagnostic or therapeutic use. Not a drug, food, cosmetic, or dietary supplement.