Localization of group-specific antigens (gs antigens) for avian leucosis-sarcoma virus complexes was studied in mouse ascites sarcoma cells (SR-C3H/He cells) induced by Schmidt-Ruppin strain of Rous sarcoma virus (SR-RSV) and in the virions of SR-RSV, using the indirect method of peroxidase-labeled antibody technique for electron microscopy. Labeled antibody used was highly specific due to purification with immunoadsorbent prepared from the corresponding antigen. The conjugates of the antibody with peroxidase was further purified by ammonium sulfate precipitation and column chromatography.
In SR-C3H/He cells, the specific reaction deposit was observed randomly throughout the cytoplasm, but not in the nucleus or plasma membrane. In SR-RSV, the deposit was found just inside the outer membrane, presumably in the zonal area between the outer and inner membranes of the virion, whereas the nucleoid and its immediate vicinity showed no reaction product. The gs antigens are thought to be localized in those areas having the specific deposit, because no specific reaction product was observed in control experiments.