Species variations in distribution of S100 in retina. Demonstration with a monoclonal antibody and a polyclonal antiserum.

The S100 protein has been found consistently in glial cells both in the central nervous system (CNS) and peripheral nervous system (PNS). However, in the retina we find substantial species variation in the distribution of this protein. Immunohistochemically, in the human retina we do not find any S100. In the rabbit retina it is present both in Müller cells and in astrocytes and in the chicken retina it is in neurons. This demonstrates how misleading it can be to use the distribution of a protein in one species to generalize about the distribution of the same protein in other species. It is also clear that even though immunohistochemical staining for the S100 protein could be used to study pathologic conditions that involve Müller cells in guinea pigs, hamster, rat, and rabbit retina it is going to be of limited value in investigations of the same conditions in the human eye.