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evidence · mechanism · dose
Experimental/AntimicrobialResearch peptide

LL-37

aka Cathelicidin

The body's endogenous antimicrobial peptide, with immunomodulatory and wound-healing roles.

Educational explainer of a research peptide. Profiles in this section deliberately omit clinical-trial citations, dosing protocols, and purchase links. Not FDA-approved as a supplement; not a recommendation to use.

Overview

LL-37 is the active fragment of human cathelicidin (hCAP-18), produced by neutrophils and epithelial cells as part of innate immunity.

Source
  • Endogenously produced
  • Synthesized for research
Forms
  • Topical
  • Subcutaneous injection (research)

Mechanism of action

Disrupts bacterial membranes directly while also modulating host immune signaling, chemotaxis, and wound-healing pathways.

Pathways
  • · Bacterial membrane disruption
  • · Chemotaxis (FPR2)
  • · Wound-healing signaling

How it acts on the body

LL-37 is one of two main classes of human antimicrobial peptides. It punctures bacterial membranes through electrostatic interactions, killing a broad range of gram-positive and gram-negative organisms, including some biofilm-resident species that resist conventional antibiotics.

Its second job is immunomodulatory: it recruits leukocytes through the FPR2 receptor, modulates TLR signaling, and accelerates re-epithelialization in wounds. Vitamin D drives endogenous LL-37 production, which is part of why vitamin D status correlates with infection resistance.

Hormonal & endocrine impact

How this peptide is reported to shift specific hormones and signaling molecules. Directionality reflects research literature and preclinical models, not clinical prescribing data.

Projected hormonal trajectory
Illustrative curves derived from reported direction of effect. Not measured patient data.

Curves are schematic shapes (sigmoid for increases/decreases, damped oscillation for modulation/stabilization) anchored to a 100% baseline. They communicate direction and tempo of change reported in research literature — not absolute hormone concentrations.

Vitamin D-dependent transcriptionModulates
Endogenous expression rises with adequate vitamin D and falls without it.
Inflammatory cytokinesModulates
Context-dependent — promotes resolution or amplifies response based on milieu.

Effects on the body

Inhibits
Broad-spectrum bacterial activity
Supports
Wound re-epithelialization
Supports
Innate immune recruitment

Organ system effects

Skin

Wound healing and infection control.

Immune System

Innate immune modulation.

Digestive / Gut

Expressed in gut epithelium as part of mucosal defense.

Reported effects

Drawn from preclinical research, anecdote, and small-scale clinical observation. No evidence grades are assigned — most peptides on this page lack rigorous human trials.

  • Activity against resistant organisms in research
  • Combined antimicrobial and pro-healing effects

Potential side effects

Common
  • · Local irritation at site of application
Rare
  • · Allergic-type reactions
Serious
  • · Pro-inflammatory if dosed inappropriately

Drug interactions

No notable interactions reported.

Pairing context

Often combined with
  • Adequate vitamin D status
    Vitamin D regulates endogenous expression.
Avoid combining with
  • Autoimmune skin disease flares
    May amplify ongoing inflammation.
Important. Research peptides described here are not FDA-approved supplements. Supplement Scholar does not endorse, recommend, or link to any source for purchase. Consult a qualified clinician before considering any peptide therapy.