ABSTRACT
Flagellum is a slender and wavy protein-attached filament on the surface of certain bacterial cells. It not only plays an important role in the movement and pathogenic ability of bacteria, but also participates in a variety of host immune regulation. Flagellin is a structural protein that forms the main part of flagellar filaments and can be recognized by TLR5 and other receptors in the host cell to induce the body′s immune response. At present, flagellin is widely used in the research of new immune adjuvants due to its immune activation, and its inflammation inhibitory effect also has good prospects against immune pathological damage. In this review, we summarized and analyzed the recent progress on the basic structure and function of flagellin, the host recognition mechanism, and its role in regulating the host immune system.