GFAP and myeloid sarcoma: In MS, AHR expression was upregulated in active and chronic MS lesions and localized to GFAP+ astrocytes; however, this might not translate into AHR-dependent downregulation of astrocyte activation, because expression of the AHR transcriptional target CYP1B1 was decreased in MS lesions and NAWM, suggesting that this pathway is defective in MS (121).