# Overview of the immunomodulatory role of bacterial probiotic-derived peptidoglycan: from molecular insights to therapeutic application

## TL;DR

This review explores how peptidoglycan from probiotics can influence the immune system and its potential for treating various diseases.

## Contribution

The paper provides a comprehensive overview of the immunomodulatory role of probiotic-derived peptidoglycan and its therapeutic potential.

## Key findings

- Probiotic-derived peptidoglycan modulates both innate and adaptive immunity.
- Peptidoglycan interacts with TLR2 and NOD1/2 to influence immune responses.
- Peptidoglycan shows therapeutic promise in treating IBD, autoimmune disorders, and cancer.

## Abstract

Probiotics are well recognized for their ability to modulate host immune responses; however, growing evidence indicates that many of their beneficial effects are mediated by structural components rather than by viable microorganisms. Among these components, probiotic-derived peptidoglycan has emerged as a key immunologically active molecule with a critical role in regulating both innate and adaptive immunity. Although substantial experimental data exist regarding its underlying mechanisms, the context-dependent immunomodulatory and anti-inflammatory functions of peptidoglycan have not been comprehensively integrated. In this review, we provide an up-to-date and comprehensive overview of the molecular and cellular mechanisms that govern the immunoregulatory properties of probiotic-derived peptidoglycan. We first discuss the structural diversity and processing of peptidoglycan and their implications for host recognition via pattern-recognition receptors, particularly Toll-like receptor 2 (TLR2) and nucleotide-binding oligomerization domain proteins 1 and 2 (NOD1/2). We then critically evaluate current evidence supporting the therapeutic potential of probiotic-derived peptidoglycan in infectious diseases, inflammatory bowel disease (IBD), autoimmune disorders, allergic inflammation, and cancer. Collectively, these findings suggest that peptidoglycan holds considerable promise for the development of next-generation microbiota-based immunotherapeutic strategies.