Glial fibrillary acidic protein (GFAP) is an intermediate filament-III protein uniquely found in astrocytes in the CNS, non-myelinating Schwann cells in the PNS and enteric glial cells. GFAP mRNA expressions are regulated by several nuclear-receptor hormones, growth factors and lipopolysaccharides.
GFAP is also subjected to a number of post-translational modifications while GFAP mutations result in protein deposits known as Rosenthal fibers in Alexander disease. GFAP gene activation and protein induction appear to play a critical role in astroglia cell activation (astrogliosis) following CNS injuries and neurodegeneration.
Emerging evidence also suggests that, following traumatic brain and spinal cord injuries and stroke, GFAP protein and its breakdown products are rapidly released into biofluids, making them strong candidate biomarkers for such neurological disorders.
Autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy is an autoimmune disease of the nervous system first defined in 2016. GFAP autoantibody, especially IgG that binds to GFAPα, has been reported in the cerebrospinal fluid (CSF) and serum of patients with GFAP astrocytopathy.
The positive predictive value of GFAP antibody in the CSF is higher than in the serum. Tissue-based assay (TBA) and cell-based assay (CBA) are both recommended methods for the detection of GFAP antibody.
GFAP astrocytopathy is accompanied by neoplasms, but the relationship between virus infection and GFAP astrocytopathy is unclear. GFAP antibody itself does not induce pathological changes; it is only a biomarker for the process of immune inflammation.