Among other important products of the kynurenine pathway, such as NAD+, the metabolites kynurenine, kynurenic acid, and xanthurenic acid are particularly relevant in the context of MS, as they serve as agonists of the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor with essential functions in immune regulation [131,132]. The gene discussed is AHR; the disease is myeloid sarcoma.