Synchronized response of CD4+ T cells to short-term dietary changes - Microbiota sequencing

Omnivorous animals, including mice and humans, tend to prefer energy-dense nutrients rich in fat over plant-based diets, especially for short periods of time. The health consequences of this short-term consumption of energy-dense nutrients remain still unclear. We found that every short-term, reiterated switches to feast diets mimicking our social eating behavior, breached the potential buffering effect of the intestinal microbiota and deeply reorganized the immunological architecture of mucosa-associated lymphoid tissues. The first dietary switch was sufficient to induce transient mucosal immune depression and suppress systemic, antigen-specific immunity leading to higher susceptibility to Salmonella Typhimurium and Listeria monocytogenes infections. This was explained by a reduction of CD4+ T cell metabolic fitness and cytokine production due to impaired mTOR activity in response to withdrawal of microbial provision of fiber metabolites. Reintroducing dietary fiber efficiently rewired T cell metabolism and restored both mucosal and systemic CD4+ T cell functions and immunity. Finally, dietary intervention study in human volunteers confirmed the impact of short-term dietary switches on human CD4+ T cell functionality. This work reveals that short-term nutritional changes cause a drastic yet transient depression of both mucosal and systemic immunity, creating windows of opportunities for pathogenic infections.