Probiotics, defined as live microorganisms that confer health benefits to the host when administered in adequate amounts, have been studied extensively for their effects on the gut-associated lymphoid tissue (GALT), including Peyer’s patches. Peyer’s patches are specialized lymphoid follicles located in the small intestine and play a crucial role in the immune surveillance of intestinal contents and the initiation of immune responses. Scientific studies have demonstrated that probiotics can modulate the activity of immune cells within Peyer’s patches, enhancing both innate and adaptive immune responses. For example, Lactobacillus and Bifidobacterium species have been shown in animal and in vitro studies to increase the number and activity of dendritic cells and IgA-producing B cells within these patches, potentially strengthening mucosal immunity.

In addition, probiotics may stimulate the production of secretory IgA, the predominant antibody isotype in the gut, via interactions with Peyer’s patches. This action helps maintain intestinal barrier function and protect against pathogenic bacteria. While much of the evidence comes from animal studies, there are also some human clinical trials indicating that probiotics can enhance specific aspects of mucosal immunity, although direct measurement within Peyer’s patches in humans is limited. Overall, the use of probiotics to support immune functions associated with Peyer’s patches is supported by a significant body of mechanistic and preclinical research, justifying a high evidence rating, even though some aspects remain to be clarified in human studies.