Purpose: The target of the antiproliferative antibody (TAPA, CD81) is a member of the tetramembrane spanning superfamily of proteins and appears to be involved in the regulation of mitotic activity and the stabilization of cellular contacts [J Neurosci 1996; 16:5478-5487]. The present study examines the distribution of this protein in the normal rat retina and its role in reactive gliosis occurring after retinal injury.
Methods: An immunoblot was used to define the relative level of TAPA in the normal rat retina. The distribution of the protein was examined using indirect immunohistochemical methods. Both of these methods were used to define the upregulation of TAPA in the rat retina injured with a needle scrape.
Results: The immunohistochemical analysis of the retina shows that TAPA is found in all layers of the normal retina with a distinct lack of labeling in the inner and outer segments of the photoreceptors. After retinal injury, a dramatic upregulation of TAPA was observed. The immunohistochemistry also revealed a pattern of expression similar to that observed in the normal retina with two notable exceptions: (1) small finger-like projections extending down into the outer segments are immunopositive, and (2) the elevated levels of TAPA can be seen outlining cell bodies in the outer nuclear layer and the ganglion cell layer.
Conclusions: TAPA is found in the normal rat retina and there is a dramatic upregulation of this protein following injury. The distribution of the protein within the retina is consistent with its expression in retinal glia, the Muller cells which span the thickness of the retina, and astrocytes found in the ganglion cell layer. These data suggest that TAPA may play a role in the proliferative response of non-neuronal cells that occurs following a mechanical injury to the retina.