Fig 2: Lesions in the NMO-rat spinal cord depends on the presence of AQP4-Ab. a–c AQP4 expression and myelin (MBP) and axon (NF-M) integrity in the spinal cord (IHC on axial and longitudinal slices, scale bars = 20 µm) of the NMO-rat, Control-rat, and rat perfused with purified IgG depleted in IgGAQP4+: NMO-ratAQP4+dep (D7). d Quantification of fluorescence intensity and axon numeration showed that AQP4-Ab depletion reduced the lesion extend in the spinal cord analyzed for AQP4 (***p < 0.001) and MBP (***p < 0.001). e Depletion reduced the amount of AQP4-Ab in IgGAQP4+dep by 40 %, as shown by flow cytometry analysis on HEK-AQP4 cells

Fig 3: Axonal damage and loss in the spinal cord and optic nerve of the NMO-rat. a Axon injury detected in the NMO-rat compared to the Control-rat (rats infused with IgGAQP4+2 and IgGControl2, D7) using neurofilament immunostaining: reduced number of axons detected as NF-M-positive spots in the white matter (WM); fragmentation and reduced axon thickness in the gray matter (GM). b Classification (10–20 to 100–140 µm2, ImageJ) and quantification (mean by field) of NF-M-positive spots in the spinal cord of the NMO-rats (n = 6) compared to the Control-rats (n = 6): loss of axons with 60–140 µm2 sections in the NMO-rats (in cart: evaluation of the total axon number, p = 0.03). c Co-detection of myelin alteration (MBP in green) and axonal loss (neurofilament NF-M subtype in red) in the spinal cord of the NMO-rat compared to the Control-rat. d Increased expression of the NF-H phosphorylated form, a marker of axon injury, detected by Western blot (pNF-H/NF-H ratio; p = 0.04). e Axon fragmentation and loss in the optic nerve of the NMO-rats compared to the Control-rat detected by NF-M immunostaining. Scale bars = 20 µm