Passive transfer of neuromyelitis optica immunoglobulin G antibody and complement via retrobulbar infusion, intravitreal injection or single perichiasmal injection does not produce optic neuritis. (A) (Top) Lateral canthotomy was done in mice to expose the optic nerve (arrow). (Bottom) Absence of binding of neuromyelitis optica immunoglobulin G antibody (NMO-IgG) (as seen using an anti-human secondary antibody) to aquaporin-4 (AQP4) in the optic nerve (dashed line) 3 days after retrobulbar infusion of NMO-IgG and human complement (representative of three eyes from separate mice). (B) Binding of NMO-IgG to AQP4 in retina (dashed line) after intravitreal injection. No binding was seen with a control (non-NMO) IgG (n = 5 eyes). (Insert) Magnified view of NMO-IgG binding to AQP4 at perivascular end-feet of inner retinal Müller cells. (C) Binding of NMO-IgG (and not of control IgG) to AQP4 after single perichiasmal injection. Despite efficient binding of NMO-IgG to AQP4 in (B) and (C), no pathology was observed after 3 days (n = 5 eyes).