Figure 5.

Mechanisms of the microbial components regulating immunity. This figure shows the role of the microbial components polysaccharide A (PSA), formyl peptide, and HBP (d-glycero-β-d-mannoheptose-1,7-bisphosphate) in the host immunity. PSA can enter the circulatory system directly through the host’s intestinal epithelial cells (IECs). In the circulatory system, PSA connects dendritic cells (DCs) and T cells through MHC class II and T-cell receptors (TCR) to inhibit inflammation. In the host’s genitourinary tract, HBP promotes the secretion of proinflammatory cytokines by the host’s immune cells through the TIFA/TRAF6/NF-κB pathway. Formyl peptide binds to neutrophils by binding to formyl peptide receptors 1 (FRR1) to regulate the inflammatory response of neutrophils.