Little or no motor disability was seen in AQP4-IgG-treated CD59+/+ rats, in control (non-NMO) human IgG-treated CD59+/+ and CD59−/− rats, and in AQP4-IgG-treated CD59−/− rats administered a complement inhibitor just before and 12 h after AQP4-IgG administration. Here, CD59 is linked to neuromyelitis optica.