Glial fibrillary acidic protein (GFAP): Purification from human fibrillary astrocytoma, development and validation of a radioimmunoassay for GFAP-like immunoactivity

The extraction and purification of glial fibrillary acidic protein (GFAP) from human fibrillary cerebellar astrocytoma is described. Using an immunoperoxidase method, antisera raised to the protein showed specific staining of astrocytes in normal spinal cord and in tumours of astrocytic origin. A double antibody radioimmunoassay for GFAP in tissue extract was developed, the detection limit of the assay being 360 pg. Extracts of tissues other than brain or spinal cord did not cross-react significantly in the assay, neither did purified preparations of myelin basic and S-100 proteins. Levels of GFAP in normal CNS tissue were highest in spinal cord (1370 μg/g wet weight) but a level of 3050 μg/g wet weight was detected in a fibrillary astrocytoma.