Capsular polysaccarides of probiotics and their immunomodulatory roles

Studies have determined the immunomodulatory activities of cell-surface polysaccharides of lactic acid bacteria(LAB)and Bacteroides;however,the mechanisms,synthesis,regulation,structure,and functional links have not been systematically discussed.We first introduce the structure of the capsular poly saccharides(CPS s)of commonly studied probiotics and Bacteroides.Wzx-Wzy dependent and ATP-binding cassette(ABC)transporter-dependent pathways are the two main biosynthesis and secretion of CPS pathways.The genes known to be associated with these two pathways are mainly those associated with priming glycosyltransferase(pGT);a variable number of genes encoding for different glycosyl transferases(GTs);Wzx/Wzy-encoding enzymes related to flippases and polymerases;and ABC-transporter genes.In addition,the effects of CPSs on host immunity as well as their related underlying mechanisms are described.Surface polysaccharides on probiotics can serve as a mask to aid in their escape from attacks from the host’s immune system.In turn,they also exhibit immunomodulatory activities,such as strengthening the functions of macrophages,promoting the maturation of antigen-presenting cells,and inducing regulatory T cells.All of these effects of cell-surface polysaccharides exhibit their significant protective properties in immunocompromised diseases,such as colitis,arthritis,and dermatitis.Finally,we focused on their structure and functional links.