Endotoxin's Impact on Organism: From Immune Activation to Tolerance and Beyond

Endotoxin, a key component of Gram-negative bacterial membranes, remains a central focus in understanding host-pathogen interactions and immune modulation. In this review, we examine the multifaceted roles of endotoxin, with particular emphasis on how its structural variants modulate host immune recognition and inflammatory signalling. We explore the complex mechanisms by which endotoxin activates innate immune pathways and how these responses evolve under repeated or chronic exposure conditions. Special attention is given to the phenomenon of endotoxin tolerance, an adaptive reprogramming of immune cells that can profoundly alter inflammatory outcomes. While this tolerance serves as a protective mechanism against hyperinflammation, mounting evidence suggests that it may have a "dark side", potentially impairing immune surveillance and promoting disease states such as cancer. We also discuss emerging clinical and therapeutic strategies that harness or counteract endotoxin-driven responses, from vaccine adjuvants to anti-sepsis interventions. By integrating recent findings from immunology, microbiology, and translational medicine, this review sheds light on the dual nature of endotoxin and its far-reaching implications for human health.