1) patients with acute NMO respond favorably to antibody-depleting Saturday October 30 th , 2010 Concurrent Symposia therapies; 2) brain MRI lesions surrounding the ventricles which are typical of NMO, localize to sites of high AQP4 expression; 3) CNS lesions in NMO exhibit deposition of immunogloblulins and products of complement activation in a vasculocentric pattern that coincides with AQP4's normal distribution; 4) CNS lesions in NMO exhibit loss of AQP4 immunoreactivity, whereas active MS lesions demonstrate upregulation of AQP4; 5) Serum IgG from patients with NMO binds to the extracellular domain of AQP4; it is predominantly IgG, and it initiates two potentially competing outcomes, AQP4 endocytosis/degradation, and complement activation; 6) Paranodal astrocytic endfeet highly express AQP4; 7)