Autoimmune Astrocytopathy

Abstract

Astrocytes are the most abundant and heterogeneous type of glial cell in the Central Nervous System. In addition to their role maintaining physiological conditions stable in the CNS, they are recognized as early and highly active players in immune responses in the CNS, and their dysfunction is believed to contribute to neuroimmune disease.

Perhaps one of the most important discoveries in recent years has been the identification of IgG-NMO, a specific pathogenic antibody directed against water channel aquaporin-4 (AQP4). IgG-NMO has not only made neuromyelitis optica diagnosis easier but has allowed differential diagnoses to be established more clearly and lead to the design of better therapeutic alternatives. Likewise, a novel autoantibody directed against GFAP has been identified as biomarker of a relapsing autoimmune form of meningoencephalomyelitis, responsive to steroids, often associated with tumors. Similarly, in Rasmussen’s encephalitis, CD8+ T lymphocytes cause astrocyte apoptosis and loss in affected areas, altering normal neuron function. Reactive astrocytes also play an important role in different CNS infections, not only during acute phases of disease but also long term, and may condition the development of post-infectious sequelae. Finally, multiple mechanisms mediated by astrocytes are known to participate in both the genesis and the progression of MS and in processes of remyelination. Overall, these observations indicate astrocytes actively participate in both pathological and in repair mechanisms, observed in CNS neuroimmune diseases.