Immune response to intestinal microbial dysbiosis

All organisms maintain intimate relationships with the microbes that live in and on their bodies, and humans are no exception. The human gastrointestinal (GI) tract harbors a complex and dynamic collection of microorganisms called the gut microbiota. Microbiome research has established that the gut microbiota is not merely a passive bystander; rather, an active participant able to impact multiple host functions, including immunity, thereby contributing to the maintenance of human health. Once perturbed, an imbalanced gut microbiota, known as gut dysbiosis, plays a pivotal role in the pathogenesis of a variety of diseases, including GI diseases, through the dysregulation of host immunity. This chapter briefly introduces the current understanding of the interplay between the gut microbiota and host immunity, emphasizing the pathogenesis of GI diseases.