[Research progress in immune recognition mechanisms and applications of bacterial flagellin]

Flagellin, the core structural protein of bacterial flagella, functions as a pathogen-associated molecular pattern (PAMP) that activates both innate and adaptive immune responses. It specifically targets signaling pathways mediated by Toll-like receptor 5 (TLR5) and the nucleotide-binding oligomerization domain-like receptor family caspase activation and recruitment domain-containing protein 4 (NLRC4) inflammasome, thereby effectively initiating and modulating the host's immune response. This review systematically outlines the dual mechanisms of immune activation by flagellin, and discusses its applications in vaccine adjuvant design, tumor immunotherapy, and allergic disease treatment. Moreover, we prospectively discuss the transformative potential of flagellin in precision immunotherapy through advanced protein engineering and targeted delivery technologies, providing a theoretical framework and practical guidance for developing novel biologic agents.