My early training in MHC molecular genetics prompted my interest in peripheral T cell tolerance mechanisms. In 1998, we discovered a link between inflammation, indoleamine 2,3 dioxygenase (IDO), and T cell regulation, establishing a new paradigm in understanding how inflammation regulates T cell immunity. We continue to study how IDO contributes to chronic inflammatory syndromes, ranging from pregnancy, chronic infections, autoimmune diseases and cancer. Key research objectives are to elucidate how IDO regulates T cell immunity and developing new reagents to treat chronic inflammatory syndromes. Based on our research, we developed IDO inhibitors and inducers to boost or suppress immunity, respectively, for clinical benefit. Current research also addresses links between inflammation, elevated IDO activity and comorbidities commonly associated with chronic diseases such as pain and depression.