The T49-550 monoclonal antibody recognizes the human Aryl Hydrocarbon Receptor (AhR), which is also known as Aromatic Hydrocarbon Receptor, and cross-reacts with the mouse AhR. AhR is a member of basic helix-loop-helix transcription factors (Class E basic helix-loop-helix protein 76, bHLHe76). AhR can bind to a variety of endogenous and exogenous ligands including tryptophan metabolites, bacterial pigments, plant flavonoids, synthetic polycyclic aromatic hydrocarbons, or dioxin-like compounds. Upon ligand binding, cytoplasmic AhR undergoes conformational changes and translocates into the nucleus to induce gene transcription. AhR is widely expressed in mammalian tissues with the highest expression levels in the liver and lung. A number of studies suggest that AhR regulates inflammation mainly by attenuating the production of inflammatory cytokines by dendritic cells and macrophages. In addition, AhR can regulate the expansion or effector functions of Th17 cells, IL-10-secreting regulatory T (Tr1) cells, and subsets of intraepithelial lymphocytes (IEL) and innate lymphoid cells (ILC), keratinocytes, and Langerhans cells.