Dietary environmental control of enteric T cell immunity - SUMMARY ABSTRACT Nutrition has a significant impact on immune health, yet mechanistic insights are lacking. Tissue-resident memory CD8 T (TRM) cells play a crucial role in mediating long-term protection against reinfection and malignancies. Because TRM are essential sentinels at the intestinal mucosa and liver, which themselves are exposed to highly dynamic nutrient environments and various enteric pathogens, understanding how diet shapes their formation and function is critical. Intestinal TRMs are situated in a unique two-front nutrient supply environment delineated by vascular supply (serosal side) and food-derived metabolites (enteral side), while liver TRM receive a mixed supply of soluble metabolites via the portal vein, mixed with lipid remnants via the hepatic artery. In both of these tissues, the unique flow of nutrients creates strong metabolic zonation. Our preliminary data show that 1) TRM positions and cytokine production in the intestine and liver are influenced by eating patterns, 2) TRM have zonated metabolic programs, and 3) intestinal TRM preferentially uptake lipids from the enteral side, while liver TRM uptake those supplied via the circulation. Aim 1 will define the nutritional control of intestinal and hepatic TRM. Using fasting, refeeding, parenteral nutrition, and defined macronutrient diets, we will determine how nutrient class, route, and timing affect TRM persistence, positioning, transcriptional states, and protective functions. Readouts will include flow cytometry, ex vivo function, subcellular-resolution spatial transcriptomics, and high-parameter multiplex immunofluorescence, all registered to tissue coordinate frameworks defined by key anatomical waypoints (crypt-villus, portal triad-central vein). Viral (LCMV) and bacterial (Listeria, Salmonella, Citrobacter) challenge models will be used to establish how diet influences TRM- mediated immunity in vivo. Aim 2 will dissect the mechanisms by which TRM adapt to dietary lipid absorption. We will investigate how the fatty acid saturation state influences TRM generation and persistence, focusing on stearoyl-CoA desaturases (Scd1/2 in mice, SCD/SCD5 in humans) as critical nodes in managing excess saturated fatty acids from the diet to preserve mitochondrial oxidative capacity under hypoxic, lipid-rich conditions. Genetic deletion using our newly developed mouse model and overexpression of Scd1/2 in murine and human T cells will establish causality. In vivo fluorescent lipid tracing, combined with spatial transcriptomics, will directly couple substrate uptake to gene programs and niche location. Functional genomics screens will identify transporters supporting lipid acquisition in situ. Mitochondrial profiling (respiration, membrane potential, fluidity, morphology) will define the cellular adaptations that safeguard intestinal TRM function in nutrient-stressed mucosal environments. Together, these studies reframe TRM biology in terms of their unique niche location, nutrient access, and tissue-specific metabolic economies, rather than systemic availability. This work will define how nutrition impacts TRM, reveal core principles of mucosal immunometabolism, and identify actionable targets for dietary intervention.
