Lactobacilli-Derived Microbe-Associated Molecular Patterns (MAMPs) in Host Immune Modulation

Although traditionally sidelined by live probiotic effects, Lactobacilli-derived Microbe-Associated Molecular Patterns (MAMPs) are emerging as potent modulators of innate and adaptive immune responses, capable of acting independently of bacterial viability. However, the underlying mechanisms remain incompletely understood. These MAMPs, such as peptidoglycan (PGN), lipoteichoic acid (LTA), and exopolysaccharides (EPSs), interact with pattern recognition receptors (PRRs) like Toll-like receptors (TLRs), initiating immune-signaling cascades that regulate cytokine production and inflammation. Lactobacilli-derived MAMPs exhibit dual immunomodulatory effects: they can enhance pro-inflammatory responses, e.g., interleukin-1β (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) under inflammatory contexts, while enhancing regulatory pathways via IL-10 and regulatory T-cell (T_regs) induction in anti-inflammatory settings. Importantly, these immunomodulatory properties persist in the absence of bacterial viability, making MAMPs promising candidates for postbiotic therapies. This opens new avenues for MAMP-based strategies to target inflammation, overcoming the risks associated with live bacterial administration. This review examines the therapeutic relevance of non-viable MAMPs, particularly in inflammatory diseases where they have demonstrated benefits in reducing tissue damage, enhancing gut barrier function, and alleviating disease symptoms. Additionally, we discuss regulatory and translational challenges hindering their clinical implementation, highlighting the need for standardized characterization, a clear safety framework, and strain-specific profiling. Given their ability to fine-tune immune responses, MAMPs represent an emerging strategy for innovative treatments aimed at restoring immune balance and reinforcing host-microbe interactions.