Fig. 2.

NMO-IgG binding internalizes M1 more efficiently than M23. (A) Distribution of AQP4 in HEK293 cells exogenously expressing M1 or M23 before and after exposure (37 °C) to NMO patient serum and representative of three experiments. Boxed region is enlarged at right. (Scale bars, 20 μm.) (B) Western blot shows AQP4 in lysates of HEK293 cells expressing M1 or M23. Actin serves as protein loading control. (C) Western blot shows AQP4 in lysates of astrocytes and control HEK293 cells. Astrocytes predominantly express M23. Exposure to NMO serum reduces M1 more than M23 (asterisk: extended autoradiographic exposure). (D) Quantification of three Western blot experiments. Bars indicate relative amounts of M1 and M23 remaining after exposure to NMO serum relative to control serum (*P = 0.003).