An initiating event in seropositive NMOSD (herein called NMO) is binding of anti-AQP4 autoantibodies (called AQP4-IgG) to AQP4 on astrocytes [27], which causes direct astrocyte injury by complement-dependent cytotoxicity (CDC) [23, 49, 54] and antibody-dependent cellular cytotoxicity (ADCC) [10, 45, 47, 63] mechanisms. This evidence concerns the gene AQP4 and neuromyelitis optica.