Mechanism
Devic's disease is similar to MS in that the body's immune system attacks the myelin surrounding nerve cells. Unlike standard MS, the attacks are not believed to be mediated by the immune system's T cells, but rather by antibodies called NMO-IgG, or simply NMO antibodies. These antibodies target the protein aquaporin 4 in the cell membranes of astrocytes which acts as a channel for the transport of water across the cell membrane. Aquaporin 4 is found in the processes of the astrocytes that surround the blood–brain barrier, a system responsible for preventing substances in the blood from crossing into the brain. The blood–brain barrier is weakened in Devic's disease, but it is currently unknown how the NMO-IgG immune response leads to demyelination.
Most research into the pathology of Devic's disease has focused on the spinal cord. The damage can range from inflammatory demyelination to necrotic damage of the white and grey matters. The inflammatory lesions in Devic's disease have been classified as type II lesions (complement-mediated demyelinization), but they differ from MS pattern II lesions in their prominent perivascular distribution. Therefore, the pattern of inflammation is often quite distinct from that seen in MS.
Read more about this topic: Neuromyelitis Optica
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