Antimicrobial Peptides and Immune Receptors Show Different Patterns Across Acne Lesion Types | Research

The takeaway

The natural antimicrobial peptides hBD-1 and cathelicidin, along with immune receptors TLR-2 and TLR-4, are expressed at significantly different levels depending on the type and severity of acne lesion.

4 distinct immune profiles
Papular, pustular, comedonal, and nodular acne lesions each showed significantly different patterns of antimicrobial peptide and immune receptor expression across skin layers.

What the researchers found

TLR-2, TLR-4, and hBD-1 expression levels differed significantly across all four skin regions examined (epidermis, dermis, inflammation area, and skin appendages) in acne lesions (p<0.05). Cathelicidin levels differed significantly only in the inflammation region.

Specifically, TLR-2 in the epidermis was lower in nodular lesions than in papules and comedones. TLR-2 in the inflammation region and dermis was significantly higher in papules compared to pustules. TLR-4 in the dermis was significantly lower in comedones compared to papules. hBD-1 in the epidermis was significantly higher in comedones compared to nodules. Cathelicidin expression in the inflammation region of comedones was significantly low.

Why it matters

Acne affects millions of people worldwide, yet treatment often relies on broad approaches like antibiotics or retinoids. Understanding that different lesion types have distinct immune and antimicrobial peptide profiles could lead to more personalized, targeted therapies. For example, treatments that boost cathelicidin in early comedonal lesions or modulate TLR-2 in inflammatory papules could be more effective than one-size-fits-all approaches.

How the study worked

Skin biopsies were collected from 80 patients with acne vulgaris — 20 each with papular, pustular, comedonal, and nodular lesions — along with 20 healthy volunteers as controls. Using immunohistochemistry, researchers measured the expression levels of TLR-2, TLR-4, hBD-1, and cathelicidin in four distinct skin areas: epidermis, dermis, inflammation region, and skin appendages. Results were compared between lesion types.

What this study cannot tell us

The cross-sectional design captures a single time point and cannot show how peptide and receptor levels change as lesions develop or resolve. The study did not control for potential confounding factors like medications, skincare products, or diet. With 20 patients per lesion type, the sample size limits statistical power for subgroup analyses. No treatment outcomes were measured, so the clinical significance of the observed differences remains theoretical.

How to read the evidence

This is an observational cross-sectional study with 100 total participants (80 patients, 20 controls). While the sample size is reasonable and the immunohistochemical methodology is standard, the cross-sectional design and lack of treatment outcomes limit causal conclusions. The statistical significance of the findings is clearly reported.

When this study was published

Published in 2016, this study contributed to the understanding of innate immunity in acne pathogenesis. More recent research has continued to explore antimicrobial peptide-based therapeutic strategies for skin conditions.

The bigger picture

Antimicrobial peptides like cathelicidin (LL-37) and human beta-defensin-1 are increasingly recognized as key players in skin health beyond just fighting infection. They modulate inflammation, wound healing, and immune signaling. This study adds to a growing body of evidence that acne is not simply a bacterial infection but a complex interplay between the skin's innate immune system, microbial communities, and inflammatory processes — with antimicrobial peptides at the center.

Questions still open

Could therapies that specifically regulate TLR-2 or cathelicidin levels improve outcomes for different acne subtypes?
How do antimicrobial peptide levels change as individual acne lesions progress from comedones to inflammatory papules or nodules?
Do current acne treatments like antibiotics or retinoids work partly by modulating these antimicrobial peptide pathways?

Common questions

What are antimicrobial peptides and what role do they play in acne?

Antimicrobial peptides are small proteins produced naturally by the body's immune system to fight infections. In the skin, peptides like cathelicidin and hBD-1 don't just kill bacteria — they also regulate inflammation and immune responses. This study shows they're expressed at different levels depending on the type of acne lesion, suggesting they help determine whether a pore becomes a blackhead, a red bump, or a deep painful nodule.

Could this research lead to new acne treatments?

Potentially, yes. By showing that different acne lesion types have distinct immune profiles involving specific antimicrobial peptides and receptors, this study suggests that targeted treatments — ones that boost or suppress particular immune molecules depending on the acne type — could be more effective than current broad-spectrum approaches. However, clinical trials would be needed to develop and validate such treatments.

Read the original research

Comparison of TLR-2, TLR-4, and antimicrobial peptide levels in different lesions of acne vulgaris.

Cutaneous and ocular toxicology, 35(4), 300-9

View on PubMed ↗Publisher’s paper ↗

Citation

Ozlu, Emin; Karadag, Ayse Serap; Ozkanli, Seyma; Oguztuzun, Serpil; Kilic, Murat; Zemheri, Ebru; Akbulak, Ozge; Akdeniz, Necmettin. (2016). Comparison of TLR-2, TLR-4, and antimicrobial peptide levels in different lesions of acne vulgaris.. Cutaneous and ocular toxicology, 35(4), 300-9. https://doi.org/10.3109/15569527.2015.1120742