LL-37

LL-37 is the sole human cathelicidin antimicrobial peptide — a 37-residue alpha-helical peptide with broad-spectrum antimicrobial activity and potent immunomodulatory properties for innate immunity research.

LL-37 is the only cathelicidin antimicrobial peptide (CAMP) found in the human genome, processed from the C-terminal domain of the 18-kDa precursor protein hCAP18 (human cationic antimicrobial protein 18) by the serine protease proteinase 3 in neutrophil azurophilic granules. The mature peptide comprises 37 amino acid residues beginning with two leucine residues (hence “LL-37”) and adopts an amphipathic alpha-helical conformation in membrane-mimetic environments. This amphipathicity — with a hydrophobic face and a cationic face — is the structural basis for its membrane-disruptive antimicrobial mechanism.

LL-37 exhibits direct antimicrobial activity against a broad spectrum of pathogens including gram-positive and gram-negative bacteria, mycobacteria, fungi (Candida species), and enveloped viruses. The mechanism involves electrostatic attraction between the cationic peptide and anionic microbial membranes (rich in phosphatidylglycerol and lipopolysaccharide), followed by membrane insertion, pore formation, and membrane disruption through carpet, barrel-stave, or toroidal pore mechanisms depending on peptide concentration and membrane composition.

Beyond direct antimicrobial activity, LL-37 is a pleiotropic immunomodulator with an extensive repertoire of host-directed functions. It acts as a chemoattractant for neutrophils, monocytes, mast cells, and T cells through formyl peptide receptor-like 1 (FPRL1/FPR2/ALX). It modulates Toll-like receptor (TLR) signaling by binding and neutralizing LPS (TLR4 ligand) and forming complexes with bacterial DNA (TLR9 ligand) or self-DNA. LL-37 promotes wound healing through EGFR transactivation via metalloproteinase-mediated HB-EGF shedding, stimulating keratinocyte and fibroblast migration. It also modulates angiogenesis through FPRL1-dependent VEGF expression and directly promotes endothelial cell proliferation.

LL-37 expression is regulated by vitamin D — the vitamin D receptor (VDR) directly transactivates the CAMP gene encoding hCAP18 — establishing a molecular link between vitamin D status and innate immune competence that has been extensively studied. LL-37 is detected in neutrophil specific granules, epithelial surfaces (skin, airways, gut, urogenital tract), and wound fluid, consistent with its role as a first-line innate defense effector.

Supplied as a lyophilized powder with ≥99% purity. Store at -20°C desiccated. For innate immunity and antimicrobial peptide research only.

Product Specifications

Certificate of Analysis

Every batch ships with a Janoshik-verified COA covering HPLC purity, mass spectrometry confirmation, and batch traceability.

Shipping & Lead Times

• US warehouse: ships within 1–2 business days · estimated 3–5 day delivery
• HK warehouse: ships within 2–3 business days · estimated 7–14 day international delivery
• Carriers: DHL Express, FedEx International, UPS Worldwide
• Discreet outer packaging — no peptide branding visible
• Tracking number emailed on dispatch

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