Hence, in the presence of NMO-IgG, low numbers of AQP4268–285-specific T cells initiate astrocyte-destructive lesions almost exclusively in spinal cord gray matter, while higher numbers of AQP4268–285-specific T cells trigger additional lesions with AQP4 and GFAP loss in the brain. The gene discussed is GFAP; the disease is neuromyelitis optica.