Aryl Hydrocarbon Receptor

Aryl Hydrocarbon Receptor (AhR) is a ligand-activated transcription factor with a helix-loop-helix motif^[1]. Mechanistically, ligand-bound AhR translocates to the nucleus, dimerizes with ARNT, and regulates transcription through xenobiotic response elements^[2]. This pathway links environmental, dietary, microbial, and metabolic small molecules to immune regulation in health and disease^[3]. In intestinal models, AhR supports gut immunity through modulation of innate lymphoid cells and intestinal barrier function^[4][5]. In T-cell disease models, AhR regulates Treg and T_H17 differentiation, connecting environmental signals with autoimmune inflammation^[6][7]. Compared with related bHLH/PAS proteins, AhR is distinguished by ligand-dependent activation, whereas AhRR lacks functional ligand-binding and transactivation domains and represses AhR signaling^[8]. For experimental applications, AhR agonists and antagonists enable pathway activation or blockade, including tapinarof in plaque psoriasis trials and CH223191 as a ligand-selective AhR antagonist^[9][10].

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