Abstract: Capsular polysaccharide (CPS) is a carbohydrate that is widely present on the surface of bacteria, mycoplasma, and some fungi. At the same time, CPS can help the bacteria resist the adverse environment such as dry and low temperature, and block the killing of host complement and phagocytosis by forming a physical barrier on the surface of bacteria. Under long-term multiple stress environments, pathogens have evolved a variety of immune escape mechanisms and promote host infection; among non-pathogenic microorganisms, CPS can positively regulate host immune function, and antagonize immune factors, to protect the host from inflammatory diseases caused by pathogens. This article will combine the relevant research works of our team to review the structure, synthesis regulatory mechanisms, biological function, immune evasion mechanism and pathogenic mechanism of CPS, especially the positive regulation of the host immune system by CPS and its application potential, to provide references for the research on pathogenic mechanisms of pathogenic bacteria and effective prevention and control of epidemic diseases.

Key words: capsular polysaccharide, regulatory mechanism of synthesis, immune escape, pathogenic mechanism, immune regulation