Lactobacillus species, as part of probiotic formulations, have been scientifically investigated for their effects on the gut-associated lymphoid tissue (GALT), which includes Peyer’s patches. Peyer’s patches are specialized lymphoid follicles in the small intestine that play a central role in the immune response to antigens present in the gut. Several animal and in vitro studies have demonstrated that Lactobacillus strains—such as L. rhamnosus, L. casei, and L. plantarum—can stimulate the activity and development of Peyer’s patches. These probiotics have been shown to enhance IgA production, modulate the balance of T-helper cells, and influence dendritic cell maturation within the GALT. Some human clinical studies also suggest that oral administration of Lactobacillus can modulate mucosal immunity, although direct measurement of their effect specifically on Peyer’s patches in humans is limited due to practical and ethical constraints.

Overall, there is moderate scientific evidence (rating: 3/5) supporting the use of Lactobacillus mixtures to influence immune function associated with Peyer’s patches, mainly based on animal and mechanistic studies. However, more robust human data are needed to fully establish clinical relevance, as most evidence comes from preclinical models.