Probiotics, postbiotics, and synbiotics in immune system modulation: A narrative review.

Interactions between the intestinal microbiota and the immune system play a crucial role in human health and the pathogenesis of various diseases. Since many beneficial effects of probiotics are mediated through their bioactive metabolites, increasing attention has been directed toward postbiotics and synbiotics as potential alternatives or complementary microbiota-based interventions. This review summarizes current evidence regarding the interactions and immunomodulatory effects of probiotics, postbiotics, and synbiotics on the human immune system. Although the immunomodulatory effects of probiotics have been extensively investigated, evidence regarding synbiotics and postbiotics remains comparatively limited and continues to evolve. A deeper understanding of the interactions between microbiota-derived bioactives and the immune system may contribute to the development of novel therapeutic strategies. This study was conducted as a narrative review based on a qualitative synthesis of the currently available literature.