AQP4 and neuromyelitis optica: This clearly shows that AQP4‐specific T cells are not only required for the formation of the pathogenic immunoglobulin isotype G1 (IgG1) of NMO‐IgG, but can also actively participate in the formation of inflammatory lesions in the CNS.14, 17 Unfortunately, to date, we do not have information about the antigen specificity of T cells found in the astrocyte‐destructive lesions of NMOSD patients.