Distribution of metallothionein in the human central nervous system

The distribution of metallothionein (MT), a metal-binding protein, was examined immunohistochemically in the normal human brain and spinal cord. Paraffin-embedded brain tissue from three patients who had died from a non-neurological disease and were free of histopathological central nervous system alterations were processed. The results of the present study demonstrate that MT is readily detectable in a subgroup of astrocytes in the normal human brain. MT staining is most intense on grey matter astrocytes that bear short stout processes and which probably represent protoplasmic astrocytes. Using anti-MT and anti-glial fibrillary acidic protein immunostaining, we could demonstrate two subpopulations of astrocytes that were mutually exclusive. The functional significance of MT-expression in protoplasmic astrocytes is not entirely clear. Metal detoxification is only one of the many postulated functions of MT. The finding that staining for MT permits subtyping of astrocytes may be of great importance in glia research and surgical pathology of the human brain.