Glial fibrillary acidic protein (GFAP) is a Type III protein that primarily exists in astrocytes within the central nervous system (CNS). However, it can also be found in other cell types such as neurons, hepatic stellate cells, kidney mesangial cells, pancreatic stellate cells, and Leydig cells. GFAP plays a role in the cytoskeleton of astrocytes and potentially in other stellate-shaped cells.

The GFAP antibody is highly valuable as a marker for identifying astrocytic cells. Moreover, many brain tumors, which are likely derived from astrocytic cells, exhibit high levels of GFAP expression. This marker is commonly employed to differentiate astrocytic neoplasms from other types of tumors within the CNS.