Lactobacillus reuteri is a probiotic bacterium that has been studied for its immunomodulatory effects, including its interactions with the gut-associated lymphoid tissue (GALT), of which Peyer’s patches are a key component. Several animal and in vitro studies suggest that L. reuteri can enhance mucosal immunity by modulating the activity and maturation of dendritic cells, increasing IgA production, and influencing T-cell differentiation within the intestinal mucosa. Peyer’s patches, which are lymphoid follicles in the small intestine, play a central role in the generation of immune responses to gut antigens. Research indicates that supplementation with L. reuteri may stimulate the activity of these patches, leading to increased antigen sampling and enhanced immune surveillance. For example, a study published in "Immunology" (2012) demonstrated that oral administration of L. reuteri in mice led to significant increases in IgA-secreting cells and upregulation of immune signaling pathways in Peyer’s patches. However, most evidence comes from preclinical models, and there is limited direct evidence in humans specifically linking L. reuteri supplementation to targeted modulation of Peyer’s patches. Overall, while promising data exist, especially from animal studies, further human clinical trials are needed to fully validate these effects.