AQP4 and neuromyelitis optica: B cells play a pathological role in NMO development and progression through a variety of mechanisms including aquaporin 4 autoantibody (AQP4-ab) production (Saadoun et al., 2010), increased proinflammatory activation, disruption of checkpoints for B cell tolerance, reduced regulatory capacity, and loss of anergy (Bennett et al., 2015).