During a T cell's development, its antigen receptor (the T cell receptor) is generated through a process of somatic cell gene rearrangement. This highly diverse, randomly generated antigen receptor repertoire present in an individual's T cell population ensures the recognition of a wide variety of pathogens, including those that the species have never previously encountered. However, the cost of this diversity is that some receptors will inevitably recognize self-antigens as well as non-pathogenic foreign antigens, such as those from commensal bacteria, with the potential to cause immune-mediated disease. The goal of my laboratory is to understand how the immune system prevents aberrant inflammatory responses to these innocuous antigens. In particular, we are interested in the development of a subset of CD4+ T cells known as regulatory T cells that are important for preventing immune activation. Understanding the development of regulatory T cells may lead to novel therapies manipulating these cells for the treatment of inflammatory conditions such as inflammatory bowel disease or autoimmune disease.