Moreover, using sera from NMO-IgG positive patients on brain tissue obtained from AQP4 knock-out mice, Lennon and colleagues [53] showed that neither human serum IgG from NMO patients nor rabbit anti-AQP4 IgG bound detectably to the AQP4 knock-out mouse brain tissues (Fig. (1)). This evidence concerns the gene AQP4 and neuromyelitis optica.