Ganglioside GD3 Immunochemistry does not Visualize Microglia but Astroglia

Ganglioside GD3, which has been used as “a marker for oligodendrocyte progenitor cells” in vitro, is present in a few cells under the ependymal lining of the ventricle in adult rat brains. However, recent studies using a monoclonal antibody against GD3(R24) suggested that GD3−positive cells in adult rat brains are microglia, thus making the cellular localization of GD3 controversial. In this immunohistochemical study, we compared images of immunostained sections of adult rat brains with a monoclonal antibody against GD3 (DSG−1) with those immunostained with microglia−specific (antibody against thymosin β4), astroglia−specific (antibodies against GFAP or S−100 protein) or with oligodendroglia−specific (antibodies against GalC or MBP) antibodies for the purpose of re−examining the identity of GD3−positive cells in adult rat brains. We observed co−localization of GD3 immunoreactivity with that of GFAP or S−100 protein, but not with that of thymosin β4, MBP or GalC. These results indicate that the GD3−positive cells in adult rat brains are astroglia, not microglia or oligodendroglia.