This, however, stands in stark contrast to an activation of AHR signaling by either FICZ (see UV Radiation-Induced Immunosuppression) or airborne PAHs and PAH-rich PM (see AHR and PAH-Induced Immune Reactions) which stimulate the generation of Th17 cells and exacerbate autoimmune disorders. The gene discussed is AHR; the disease is Autoimmunity.