Research progress on the structure-activity relationship and action mechanisms of polysaccharides with immunomodulatory activity

With the change of modern lifestyle, low immunity has become a health problem faced by more and more people. Hence, the development of natural active products with immunomodulatory activity has become one of the current hot research issues. Polysaccharides have attracted much attention in immunomodulatory activity due to their rich sources, good safety, few side effects, and stable therapeutic effects. Currently, existing research on immunoactive polysaccharides still has deficiencies and fails to fully clarify their multi-level regulatory mechanisms and structure-activity relationships. Therefore, this article systematically reviews the relationship between polysaccharide structure (molecular weight, monosaccharide composition, glycosidic bonds, substituent, and high structure) and immunomodulatory activity. Moreover, this review systematically summarizes the immunoregulation action mechanisms of polysaccharides from three aspects including immune system regulation, immunomodulatory receptors, and the regulation of intestinal flora. Furthermore, the challenges of current studies on the immunomodulatory activity of polysaccharides and future research directions were discussed. The results can enhance the understanding of polysaccharides with immunomodulatory activity from different resources, which provides theoretical support for the development and application of polysaccharides as dietary supplements and their precision nutrition strategies.