Although neutrophils and eosinophils comprise the predominant cell types within NMO lesions, T cells are also detected.6, 35 As it is recognized that NMO IgG alone does not induce CNS inflammation and Th17 cells can promote tissue accumulation of neutrophils, AQP4-specific T cells may be sentinel adaptive immune cells directing CNS inflammation in NMO. This evidence concerns the gene AQP4 and neuromyelitis optica.