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Eldon E. Geisert, Haley J. Abel, Liying Fan, Grace R. Geisert; Retinal Pigment Epithelium of the Rat Express CD81, the Target of the Anti-proliferative Antibody (TAPA). Invest. Ophthalmol. Vis. Sci. 2002;43(1):274-280.
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purpose. The present study focuses on the role of CD81, the target of the
anti-proliferative antibody (TAPA), in the regulation of the growth of
retinal pigment epithelium (RPE).
methods. RPE of 8-day-old rat pups was cultured. The level of CD81 in the
cultures was defined by immunoblot methods, and the distribution of the
protein was examined using indirect immunohistochemical methods. In
addition, the effects of the antibody binding were tested in culture.
results. CD81 was found in all layers of the normal retina with a distinct
absence of labeling in the inner and outer segments of the
photoreceptors. Based on the authors’ original immunohistochemical
analysis, it was difficult to determine whether CD81 was
expressed by RPE. By examining cultures of RPE it was demonstrated that
CD81 was expressed on the surface of these cells and that it was
concentrated at regions of cell–cell contact. Indirect
immunohistochemical methods using a peroxidase-labeled secondary
antibody in albino mice revealed heavy labeling of the RPE in the
intact eye. When the AMP1 antibody (directed against the large
extracellular loop of CD81) was added to cultured RPE, the mitotic
activity of the cells was depressed.
conclusions. CD81 was found in the normal rat retina. Previous studies demonstrated
that CD81 was expressed in retinal glia, the Müller cells that
span the thickness of the retina, and astrocytes found in the ganglion
cell layer. The present study demonstrated that CD81 was also expressed
by RPE. The dramatic effects of the AMP1 antibody and the location of
CD81 at regions of cell–cell contact support the hypothesis that this
molecule is part of a molecular switch controlling contact
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