The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor and member of the basic helix-loop-helix Period-ARNT (AHR nuclear translocator)-Single-minded protein family. The AHR is best known for mediating the toxic effects of the environmental contaminant, 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD). Some of which include dysregulated lipid and glucose metabolism, carcinogenesis and dysfunction of the immune, reproductive and nervous systems . However, the precise molecular mechanisms are not well established. AHR also regulates responses of numerous anthropogenic and natural chemicals, including several endogenous and dietary compounds , most of which do not cause TCDD-like toxicity. Recently, additional roles for AHR in adaptive drug metabolism, differentiation, vasculature development and in the modulation of regulatory T cells (Tregs) and proinflammatory T helper 17 (Th17) cells have been reported [3,4]. These findings have prompted intense interest in exploring AHR as a therapeutic target for cancer, autoimmune and other human diseases . Understanding the molecular mechanisms of AHR signaling will provide a better appreciation of its biological role, its utility as a therapeutic target and the relationship between TCDD-exposure and human disease.