Lactobacillus species are well-known probiotics that have been studied for their effects on gut-associated lymphoid tissue (GALT), which includes Peyer's patches. Peyer’s patches are lymphoid follicles in the small intestine that play a critical role in immune surveillance and the generation of immune responses to antigens present in the gut. Scientific studies have shown that certain strains of Lactobacillus can modulate immune responses in the gut, including increasing the number and activity of immune cells within Peyer’s patches. For example, animal studies have demonstrated that administration of Lactobacillus casei or Lactobacillus rhamnosus can enhance IgA production and stimulate dendritic cell and T cell activity in Peyer’s patches (Matsuzaki & Chin, 2000).

Human data are more limited, but some clinical research suggests that oral supplementation with Lactobacillus can influence mucosal immunity, potentially via mechanisms involving Peyer's patches. Nonetheless, most direct evidence comes from animal models or in vitro studies. The immunomodulatory effects appear to be strain-specific and may not apply to all Lactobacillus species. Therefore, while there is scientific support for an interaction between Lactobacillus and Peyer’s patches, especially in preclinical studies, the overall evidence is moderate and not yet definitive in humans.