Oral microbiota–driven immune modulation along the oral–gut axis: from local signals to systemic inflammation

The oral-gut axis is a key pathway through which oral microbiota modulate systemic immunity. Oral bacteria and their derivatives, including microbial-associated molecular patterns and extracellular vesicles, can translocate to the gut, evade mucosal defenses, interact with local immune cells, and disrupt epithelial integrity. This review highlights mechanisms of gut colonization, immune modulation via pattern recognition receptors, and contributions to distal organ inflammation, providing a framework for understanding microbiota-driven systemic diseases.