AHR and psoriasis: Examples of AhR ligand promiscuity are Tapinarof (3,5-dihydroxy-4-isopropylstilbene), a nonsteroidal drug, approved by the US Food and Drug Administration in 2022 for the treatment of psoriasis [9] and indole-3-carboxaldehyde (3-IALD), an endogenous tryptophan microbial metabolite that received the orphan drug designation in 2023 by the European Medicines Agency for the treatment of primary Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) checkpoint-related immunodeficiencies [10].