Immunohistochemical localization of intermediate filament and S-100 proteins in several non-endocrine cells of the human pituitary gland.

The presence and distribution of glial fibrillary acidic protein, vimentin, neurofilament protein, cytokeratins No. 8 (52 Kd), No. 18 (45 Kd) and No. 19 (40 Kd) and S-100 protein in pituicytes, folliculo-stellate cells, the epithelium of the Rathke's cysts and squamous cell nests of the pars tuberalis were investigated immunohistochemically by the peroxidase-antiperoxidase (PAP) method in eleven normal human pituitary glands. An identical immunostaining pattern was expressed by both folliculo-stellate cells and pituicytes. In both cell types the immunostaining for glial fibrillary acidic protein (GFAP), S-100 protein and vimentin was strongly positive. These results indicate the probable glial origin of the folliculo-stellate cell, and enlarge the group of glial cell types expressing vimentin. The co-expression of cytokeratins No. 8 and 19, both characteristic for simple epithelia, and S-100 protein was evident in the epithelial cells lining the Rathke's cysts and the squamous cell nests of the pars tuberalis. Furthermore, some epithelial cells of the Rathke's cysts co-expressed cytokeratins, S-100 protein and GFAP, a fact seldom reported and only in relation to rare neoplasms. The cytokeratin No. 18, characteristic for glandular epithelia, was not clearly demonstrated. Finally, the neurofilament protein was detected only in axons of the neurohypophysis; no immunopositive cells could be found throughout the adenohypophysis. Similarities in the antigenic patterns of these cell populations and the possible relation with their origin and nature are discussed.