AQP4 and Autoimmunity: Although the etiology and mechanisms triggering AQP4 autoimmunity and the production of AQP4-IgG autoantibodies in NMOSD are uncertain, B cells definitely have important roles in the pathophysiologies, as the production of pathogenic high affinity AQP4-IgG requires memory B cells autoreactive to AQP4 to differentiate to plasmablasts and mature plasma cells (antibody secreting cells (ASC)), which produce AQP4-IgG [38].