Brain Immunohistopathology in a Patient with Autoimmune Glial Fibrillary Acidic Protein Astrocytopathy.

BACKGROUND: Autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy is a novel meningoencephalomyelitis. However, the pathogenesis of this disease is unclear. We therefore examined a brain biopsy from a patient with autoimmune GFAP astrocytopathy by immunohistopathology.

METHODS: We examined brain biopsy sections from a patient with autoimmune GFAP astrocytopathy using hematoxylin and eosin (HE) and Luxol fast blue (LFB) staining, and immunostaining with antibodies for CD4, CD8, CD3, CD20, CD68, CD138, Neu-N, GFAP, myelin oligodendrocyte glycoprotein (MOG), and aquaporin-4 (AQP4).

RESULTS: HE staining revealed extensive inflammatory cells (marked lymphocytes) around brain vessels, and LFB showed no signs of demyelination or axon loss. Immunohistochemical analysis showed CD3+ and CD4+ T cells cuffing around brain vessels, accompanied by CD8+ T cells, CD20+ B cells, and CD138+ plasma cells, while some macrophages (CD68+) were scattered throughout the brain parenchyma. There was no loss of AQP4 or MOG expression in this patient, while GFAP was abundantly expressed.

CONCLUSIONS: These findings suggest that inflammatory cells, including T cells, B cells, plasma cells, and macrophages, are involved in autoimmune GFAP astrocytopathy. Demyelination and astrocyte loss may not necessarily occur in this disease.