Immunohistochemical study of cells positive for glial fibrillary acidic protein (GFAP) in the human pituitary gland, with special reference to folliculo-stellate cells.

The cytology and the distribution of cells which contain glial fibrillary acidic protein (GFAP) were studied immunohistochemically in thick frozen sections of human pituitary glands. Immunoreactive cells were constantly demonstrated in both neuro- and adenohypophysis. In the neural lobe, an irregular network of long GFAP-positive pituicyte processes was revealed. Within this network, some asymmetric pituicytes became visible. A variable number of cells was stained in cell cords and follicles of the pars distalis and the intermediate zone. The morphology of these cells could be studied in detail, providing strong evidence to support the hypothesis that adenohypophyseal GFAP-immunoreactive cells belong to the folliculo-stellate (FS) cell system. Cells with similar cytological features in the pars distalis or the intermediate zone were found to share common immunoreactivities against GFAP and the presumable FS cell markers vimentin and S-100 protein. Our results corroborate the notion that, in the human pituitary, GFAP can be regarded as a marker protein of pituicytes and FS cells, which is expressed at varying degrees.