The broad, long-term objective of research in Dr. William’s laboratory is to establish the mechanisms that promote T cell development in the thymus and maintain T cell tolerance in the periphery. He has placed special emphasis on role of Foxp3+ regulatory T (Treg) cells, and have developed a number of mouse models that are widely used to study Treg cell function. Dr. Williams has a broad background in immunology, with specific training in basic science and translational investigation. As a postdoctoral fellow with Paul Allen at the Washington University School of Medicine, he investigated the role of ligand affinity in shaping the T cell repertoire during thymic development. In 2002, he was appointed Section Chief of Pediatric Rheumatology at the Medical College of Wisconsin, where he has developed the rheumatology clinical service and established a fellowship program. In 2013, he was appointed as the Chief Scientific Officer of the Children’s Research Institute. In this role Dr. William’s coordinates the pediatric research portfolio at the Medical College of Wisconsin and Children’s Wisconsin campus and directs research investment. As a Principal Investigator on grants from the NIH and the March of Dimes, he describes T cell receptor antagonism as potent mechanism of peripheral tolerance. With additional funding from the NIH, Children’s Wisconsin and the Crohn’s and Colitis Foundation, he expanded his research program to investigate the role of different types of Treg cells and the mechanisms of Treg cell-mediated suppression in models of inflammatory autoimmune disease. Our work has led to the identification of induced Treg cells that produce IL-10 as an essential regulatory subset.