Immune responsiveness and antigen specific recognition of intestinal microbes must be tightly regulated. Unnecessary inflammation that can support conditions such as inflammatory bowel disease must be avoided while rapid responses to microbes that breach the epithelial barrier must be allowed. We are interested to understand this regulation and have identified an early life developmental window where intestinal microbes are trafficked to the thymus where naive T cells that recognize them are then expanded. These microbiota specific T cells can protect in infection models or induce pathology in models of inflammatory disease models. We are continuing to work to understand the peripheral role for these cells throughout life as well as the developmental changes into adulthood regulating these processes.