H2AX and neuromyelitis optica: Exposure of astrocytes to sera from seropositive NMO patients resulted in significantly higher percentages of H2AX-expressing cells compared with the exposure to sera of HCs and no sera (30.3 ± 2.2%, 10.6 ± 3.4%, and 1.7 ± 0.6%, p < 0.0001, Figure 3d,e).