Propionibacterium freudenreichii subsp. shermanii is a probiotic bacterium traditionally used in cheese production (such as Emmental) and has recently attracted scientific interest for its immunomodulatory properties. Research over the last decade indicates that this bacterium can interact with the gut-associated lymphoid tissue (GALT), which includes Peyer’s patches—specialized lymphoid follicles in the small intestine that play a key role in mucosal immunity.

Several in vitro and animal studies (for example, Rabah et al., 2017, Frontiers in Microbiology) have shown that P. freudenreichii can modulate immune responses by stimulating the production of anti-inflammatory cytokines (such as IL-10) and enhancing the function of regulatory T cells. These effects are believed to be mediated, at least in part, by the production of short-chain fatty acids (like propionate) and by bacterial surface proteins that interact with immune cells in Peyer’s patches.

However, while laboratory and animal research is promising, human clinical trials directly demonstrating benefits on Peyer’s patches or mucosal immunity are limited. Most human studies focus on general gut health and immune markers rather than direct effects on Peyer’s patches. Thus, the evidence is scientific in nature, but current support is moderate and based mainly on mechanistic and preclinical data.