FICZ is a potent endogenous ligand for the aryl hydrocarbon receptor (AhR), making it a key molecule in studying immune regulation and inflammatory responses. It is widely used in research to activate AhR signaling pathways, which play a role in maintaining immune homeostasis, particularly in T cell differentiation and suppression of autoimmune responses. FICZ has been shown to promote the development of regulatory T cells and modulate dendritic cell function, suggesting its potential in understanding autoimmune diseases such as multiple sclerosis and inflammatory bowel disease. Due to its ability to induce cytochrome P450 enzymes, it is also used as a tool compound in studies of xenobiotic metabolism. Its photosensitivity and rapid metabolism make it ideal for short-term, high-intensity pathway activation in cell culture models.