Considering the fact that AQP4 contains a large number of potential T cell epitopes, not only in mice and rats [12, 25, 32], but also in humans [6, 23] (Fig. 1), it is tempting to speculate that this might be a strong argument in favor of very early T cell vaccination, and a strong counter-argument for later T cell vaccination as a therapeutic option for NMO patients. This evidence concerns the gene AQP4 and neuromyelitis optica.