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LL-37

A naturally occurring antimicrobial peptide that plays a key role in innate immune defense.

EmergingLimited Data

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This information is for educational purposes. Peptide therapy should be guided by a licensed healthcare provider. Connect with a Noho clinician

What is LL-37?

LL-37 is a 37-amino-acid peptide that is the only cathelicidin-derived antimicrobial peptide found in humans. It is produced by immune cells, epithelial cells, and other tissues as part of the innate immune response. It has broad-spectrum antimicrobial activity against bacteria, viruses, and fungi, and also modulates inflammation and wound healing.

Why People Talk About It

Immune system support

Emerging

Antimicrobial defense

Moderate

Gut barrier support

Preliminary

Wound healing

Preliminary

How It Works

LL-37 is part of your body's natural defense system. It can directly kill bacteria and viruses by disrupting their membranes, and it also signals immune cells to respond to threats. Think of it as both a weapon and a signal flare for your immune system.

Common Questions

Safety Information

Important Safety Notes

Common Side Effects

Injection site reactionsPotential for immune activation

Cautions

  • Limited data on exogenous administration
  • Potential for excessive immune activation
  • Not FDA-approved for therapeutic use

What We Don't Know

The effects of exogenous LL-37 administration are not well characterized in humans. Optimal dosing and safety parameters are not established.

Published Research

35 studies

Associations between vitamin D status and biomarkers linked with inflammation in patients with asthma: a systematic review and meta-analysis of interventional and observational studies

Meta-AnalysisPMID: 39322954

Impact of vitamin D status and cathelicidin antimicrobial peptide on adults with active pulmonary TB globally: A systematic review and meta-analysis

Meta-AnalysisPMID: 34115790

The Multifunctional Roles of Short Palate, Lung, and Nasal Epithelium Clone 1 in Regulating Airway Surface Liquid and Participating in Airway Host Defense

Meta-AnalysisPMID: 33885339

Transcriptional Profiling of Mycobacterium tuberculosis Exposed to In Vitro Lysosomal Stress

Meta-AnalysisPMID: 27324481

Acute effects of continuous and interval cycling on salivary SIgA and anti-microbial peptide secretions: a randomized crossover trial

Randomized Controlled TrialPMID: 40810749

Limosilactobacillus fermentum LF61: A multidimensional study on safety and functionality from genomics to clinical application

Randomized Controlled TrialPMID: 41655688

The Immunomodulatory Activity of High Doses of Vitamin D in Critical Care Patients with Severe SARS-CoV-2 Pneumonia-A Randomized Controlled Trial

Randomized Controlled TrialPMID: 39940396

Impact of 3-dimensional myofascial release on tumor necrosis factor (TNF) alpha biomarker in nonspecific low back pain: a randomised controlled trial

Randomized Controlled TrialPMID: 40853451

Effect of weekly vitamin D supplementation on the severity of atopic dermatitis and type 2 immunity biomarkers in children: A randomized controlled trial

Randomized Controlled TrialPMID: 38483248

Outcomes of High-Dose Versus Low-Dose Vitamin D on Prognosis of Sepsis Requiring Mechanical Ventilation: A Randomized Controlled Trial

Randomized Controlled TrialPMID: 38706151

Weekly Vitamin D Supplementation to Prevent Acute Respiratory Infections in Young Children at Different Latitudes: A Randomized Controlled Trial

Randomized Controlled TrialPMID: 39181322

Acute salivary antimicrobial peptide secretion response to different exercise intensities and durations

Randomized Controlled TrialPMID: 39155711

Efficacy and safety of Oral LL-37 against the Omicron BA.5.1.3 variant of SARS-COV-2: A randomized trial

Randomized Controlled TrialPMID: 37605995

Efficacy of LL-37 cream in enhancing healing of diabetic foot ulcer: a randomized double-blind controlled trial

Randomized Controlled TrialPMID: 37480520

Reduction of Erythema in Moderate-Severe Rosacea by a Low Molecular Weight Heparan Sulfate Analog (HSA)

Randomized Controlled TrialPMID: 37276169

Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trial

Randomized Controlled TrialPMID: 34687253

A randomized controlled trial on the coloprotective effect of coenzyme Q10 on immune-inflammatory cytokines, oxidative status, antimicrobial peptides, and microRNA-146a expression in patients with mild-to-moderate ulcerative colitis

Randomized Controlled TrialPMID: 33620550

Dose effect of bovine lactoferrin fortification on diarrhea and respiratory tract infections in weaned infants with anemia: A randomized, controlled trial

Randomized Controlled TrialPMID: 34102559

Functional Antibodies and Innate Immune Responses to WRSS1, a Live Oral Shigella sonnei Vaccine Candidate, in Bangladeshi Adults and Children

Randomized Controlled TrialPMID: 34374425

The therapeutic efficacy of Bifidobacterium animalis subsp. lactis BB-12(®) in infant colic: A randomised, double blind, placebo-controlled trial

Randomized Controlled TrialPMID: 31797399

Seasonal Antimicrobial Activity of the Airway: Post-Hoc Analysis of a Randomized Placebo-Controlled Double-Blind Trial

Randomized Controlled TrialPMID: 32867053

Vitamin D and Phenylbutyrate Supplementation Does Not Modulate Gut Derived Immune Activation in HIV-1

Randomized Controlled TrialPMID: 31330899

Reduction of respiratory infections in asthma patients supplemented with vitamin D is related to increased serum IL-10 and IFNγ levels and cathelicidin expression

Randomized Controlled TrialPMID: 29402723

Serum level of cathelicidin LL-37 in patients with active tuberculosis and other infectious diseases

Randomized Controlled TrialPMID: 28956425

Cow's milk and rice fermented with Lactobacillus paracasei CBA L74 prevent infectious diseases in children: A randomized controlled trial

Randomized Controlled TrialPMID: 26732025

Impact of high-dose vitamin D(3) on plasma free 25-hydroxyvitamin D concentrations and antimicrobial peptides in critically ill mechanically ventilated adults

Randomized Controlled TrialPMID: 28526374

Effect of Cholecalciferol Supplementation on Vitamin D Status and Cathelicidin Levels in Sepsis: A Randomized, Placebo-Controlled Trial

Randomized Controlled TrialPMID: 26086941

Significant Effects of Oral Phenylbutyrate and Vitamin D3 Adjunctive Therapy in Pulmonary Tuberculosis: A Randomized Controlled Trial

Randomized Controlled TrialPMID: 26394045

Nasal Levels of Antimicrobial Peptides in Allergic Asthma Patients and Healthy Controls: Differences and Effect of a Short 1,25(OH)2 Vitamin D3 Treatment

Randomized Controlled TrialPMID: 26545199

Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial

Randomized Controlled TrialPMID: 25041740

Cathelicidin LL-37: a multitask antimicrobial peptide

ReviewPMID: 20049649

LL-37, the only human member of the cathelicidin family of antimicrobial peptides

ReviewPMID: 16716248

The roles of cathelicidin LL-37 in immune defences and novel clinical applications

ReviewPMID: 19068548

A comprehensive summary of LL-37, the factotum human cathelicidin peptide

ReviewPMID: 23246832

Therapeutic Potential of Cathelicidin Peptide LL-37, an Antimicrobial Agent, in a Murine Sepsis Model

PreclinicalPMID: 32825174

Always consult a qualified clinician

This information is for educational purposes. Peptide therapy should be guided by a licensed healthcare provider. Connect with a Noho clinician

Research Insights

Related Peptides

Quick Facts

Class
Antimicrobial Peptide
Evidence
Emerging
Safety
Limited Data
Updated
Jan 2026
Citations
35PubMed

Also known as

CathelicidinHuman Cathelicidin Antimicrobial Peptide

Tags

Immune SupportAntimicrobialGut HealthInflammation

Related Goals

Evidence Score

Overall Confidence40%

Clinical Trials

View Clinical Trials

Links to ClinicalTrials.gov for reference. Listing does not imply endorsement.

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