In active NMO patients with AQP4 autoantibodies (AQP4-IgG), there is a prominent expansion of CSF plasmablast clones in the absence of corresponding CSF OCBs (44, 45) and only 60% of infiltrating plasmablast clones are targeted against conformational AQP4 epitopes (44). This evidence concerns the gene AQP4 and neuromyelitis optica.