Microbiome-mediated T cell regulation, inflammation, and disease

The human gastrointestinal tract harbors trillions of microorganisms. These microorganisms contribute intricately to regulate local homeostatic processes and in the development and function of the host immune system. This chapter gives a good account of our comprehension of the development and composition of the human intestinal microflora, and its potential impact on gut integrity and human health. Outlined in Fig. 16.1, we emphatically summarize the recent findings to demonstrate how the gut microbiome is influenced by food and dietary fiber. Later, we will also present how various proinflammatory and antiinflammatory metabolites (TMAO, FFA, SCFAs, BA, etc.) regulate T cell differentiation (Tregs versus Teff), which eventually dictates inflammation, obesity, immunity, and tolerance. In addition, we aim to encapsulate the recent findings to elaborate on how specific gut microbiota and its bioactive metabolites are indispensable in shaping the balance between inflammatory Th17 effector and regulatory Treg cells. Furthermore, we address how the disbalance of gut microbiome composition is associated with health and diseases and clinical intervention of healthy fecal microbiota transplantation regulates and restores the ratio of Th17 and Treg cells.