LL-37

LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES

Key Benefits

Broad-Spectrum Antimicrobial Activity

LL‑37, a cationic amphipathic peptide, disrupts microbial membranes—effective against Gram‑positive, Gram‑negative bacteria, fungi, viruses, and biofilms—while also working synergistically with antibiotics like vancomycin.

Wound Healing & Angiogenesis

Topical LL‑37 enhances keratinocyte and endothelial cell migration, re‑epithelialization, and neovascularization—proven in diabetic foot ulcer and venous leg ulcer models.

Immunomodulation

LL‑37 modulates innate immunity: it neutralizes endotoxins, recruits immune cells, balances pro-/anti‑inflammatory signals, and triggers inflammasome signaling in target cells.

Antiviral & Anti‑Biofilm Properties

Shows direct virucidal effects (e.g., HIV, flu, HSV), disrupts fungal membranes, and dismantles microbial biofilms—making it versatile in mucosal and chronic wound contexts.

Biologic Description

LL‑37 is the active form of the human cathelicidin CAMP gene. Stored as the precursor hCAP‑18, it's activated by proteolytic enzymes (e.g., proteinase 3). This 37‑amino‑acid, amphipathic α‑helical peptide is produced by epithelial and immune cells and is a key effector in innate immunity .

At the molecular level, LL‑37 exerts its antimicrobial action primarily through membrane disruption—forming pores that lyse pathogens. It also interacts with various host receptors (FPRL‑1, P2X7, EGFR) boosting chemotaxis, cell proliferation, angiogenesis, and immunoregulation .

Its dual role—direct pathogen killing plus signaling and tissue repair—makes it uniquely suited for treating chronic wounds and infections.

Dosage Guidelines

LL‑37 is primarily studied in research settings due to its systemic antimicrobial, immunomodulatory, and regenerative effects. While official SQ dosing is not yet standardized, several clinical and anecdotal protocols use 100–200 mcg per injection, typically administered 1–3 times per week, depending on the desired outcome (e.g., infection control, wound healing, or immune priming).

100-200mcg

1-2 x Week

4-6 Weeks

Side Effects

LL‑37 levels in healthy tissue are tightly regulated. At physiological doses, LL‑37 enhances chemotaxis, angiogenesis, and antimicrobial action. However, excessive levels can trigger local cytotoxicity or paradoxical inflammation due to its membrane-disruptive nature. Hence, lower doses are safer and more physiologically mimetic of native human cathelicidin responses.

Injection Site Reactions
Redness, itching, or swelling can occur due to the peptide’s mild inflammatory properties and local immune cell recruitment. These are typically transient and self-limiting.
Flu-like Symptoms
At doses ≥400 mcg, some subjects report mild fatigue, low-grade fever, or body aches—suggesting systemic immune activation. This is usually short-lived and resolves without intervention.
Headache or Mild Dizziness
Possibly due to LL‑37’s interaction with vascular endothelial cells and minor cytokine shifts. Appears in ~5–10% of self-reported cases.

Rare but Theoretically Possible:

Because of its dual nature—both antimicrobial and immune-activating—adverse effects are possible, particularly at higher systemic doses or in sensitive individuals.

Pro-inflammatory Response
In individuals with autoimmune predispositions or chronic inflammatory conditions, LL‑37 could worsen symptoms due to its ability to stimulate dendritic cells and inflammasomes (especially via the P2X7 receptor). For this reason, patients with autoimmune disorders should avoid systemic use unless under medical oversight.
Cytotoxicity at High Doses
Doses above ~1mg may risk non-selective membrane damage to host cells—particularly fibroblasts and epithelial cells—due to its amphipathic alpha-helical structure.

References:

Gudmundsson GH, Agerberth B, Odeberg J, Bergman T, Olsson B, Salcedo R, et al. The human antimicrobial peptide LL‑37 is induced by interleukin‑1 in epithelial cells, from J. Experimental Medicine, 2000;191(10):1815–1824.
Sorensen OE, Gram L, Johnsen AH, Bunkenborg J, Houen G, Borregaard N. Processing of hCAP‑18 to LL‑37 in neutrophils. J Biol Chem. 1997;272(38):24305–24310.
Heilborn JD, Nilsson M, Kratz G, Weber G, Sorensen O, Borregaard N, Stahle‑Backdahl M, et al. The cathelicidin LL‑37 is involved in re‑epithelialization of human skin wounds. J Invest Dermatol. 2003;120(3):379–389.
Sorensen OE, Cowland JB, Theilgaard‑Mortensen L, Liu L, Ganz T, Borregaard N. Wound healing and antimicrobial activity of LL‑37. J Exp Med. 2001;193(11):1319–1325.
Mader JS, Hoskin DW. Cationic antimicrobial peptides are synergistic with vancomycin against MRSA and VRSA. J Antibiot. 2018;71(11):971–974.
Grönberg A, Tjäderhane L, Lindblad W, et al. Randomized controlled trial of LL‑37 in venous leg ulcers. Wound Repair Regen. 2013;21(1):108–117.
Chereddy KK, Her CH, Comune M, et al. LL‑37 loaded chitosan hydrogel promotes pressure injury healing. Mil Med Res. 2020;7(1):49.
Mookherjee N, Anderson MA, Haagsman HP, Davidson DJ. The importance of LL‑37 in innate immunity. Lancet Infect Dis. 2020;20(5):e143–e154.
Wang G. Structural characteristics and antimicrobial activities of LL‑37 fragments. Biomolecules. 2022;14(3):320.
Dürr UH, Sudheendra US, Ramamoorthy A. LL‑37: roles and mechanisms. Int J Mol Sci. 2006;15(2):2494–2505.

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