AQP4 and autoimmune disease: Immunofluorescence analysis showed that treatment with hsAQP4-IgG, but not hsCtrl-IgG or LPS, lead to the internalization and degradation of AQP4 in astrocytes (Fig. 1d), which is a hallmark of NMO pathology that distinguishes NMO from the autoimmune disease multiple sclerosis19.