Physiological functions of the aryl hydrocarbon receptor in innate and adaptive immune responses. (360G-Wellcome-100910_Z_13_Z)

The aryl hydrocarbon receptor (AhR), a ligand dependent transcription factor best known for mediating the toxic effects of xenobiotics, has recently been shown to play important roles in the immune system, although mechanistic insight is lacking. AhR is expressed in a wide range of haematopoietic cells, but also on epithelial cells interfacing with the environment, eg skin, lung, intestine. We plan to investigate the physiological functions of AhR in the immune system by generating AhR-FTAP mice to identify protein interactions with AhR in different cells types and immunological conditions to gain mechanistic insight into how AhR works. Furthermore, we will focus on the physiological regulation of AhR signaling via metabolic enzymes such as CYP1A1 that are induced by AhR activation and subsequently metabolise the agonist in a negative feedback loop. Mice with targeted deletion of the three CYP enzymes under control of AhR show increased AhR stimulation and have a range of immunological phenotypes, which we plan to explore, using infection/inflammation models targeting skin, lung or intestine. AhR deficient mice on the other hand show hyperinflammatory reactions, suggesting that interference with the regulation of AhR activation adversely affect homeostasis at these barrier sites. Analysis of mice with cell type specific AhR deletion will identify cell intrinsic consequences of defective AhR signalling. We furthermore plan to generate mice overexpressing CYP1A1 to test the hyp othesis that rapid degradation of physiological AhR ligands may result in dysregulation of immune responses at mucosal barriers sites.