TET Enzymes as Epigenetic Integrators in Intestinal Immunity, Inflammation, and Disease.

DNA methylation plays a fundamental role in maintaining intestinal homeostasis, immune tolerance, and inflammatory balance. Active DNA demethylation, mediated by the ten-eleven translocation family of dioxygenases (TET1, TET2, and TET3), has emerged as an important epigenetic mechanism linking environmental and metabolic cues to gene regulatory programs in the gut. In the intestinal epithelium, TET-dependent DNA hydroxymethylation contributes to intestinal stem cell maintenance, epithelial differentiation, regeneration, and barrier integrity. Perturbations in TET activity are associated with epithelial dysfunction, chronic inflammation, and increased susceptibility to colorectal tumorigenesis. Within the immune compartment, TET-mediated demethylation is required for the epigenetic stabilization of gut-associated immune cells. Altered TET function has been implicated in immune imbalance in inflammatory bowel disease, Hirschsprung's disease, and colitis-associated colorectal cancer. Emerging evidence further indicates that intestinal microbiota-derived metabolites, including short-chain fatty acids and aryl hydrocarbon receptor ligands, modulate TET activity, positioning TET enzymes as epigenetic sensors of microbial and metabolic signals. In turn, TET-dependent programs shape immune responses to commensal microbes and pathogens, establishing a bidirectional microbiota-epigenetic axis that influences both intestinal and systemic immunity. In this review, we summarize and critically evaluate current evidence on the roles of TET enzymes in intestinal epithelial biology, immune cell regulation, and host-microbiota interactions in colorectal inflammation and disease.