Retention of MMTV virions on the cells surface of IFNα treated cells. GR cells were treated with vehicle (left panels) or IFNα (right panels) for 24 hours and then processed for scanning (A and B) or transmission (C and D) electron microscopy. MMTV virions with a distinct capsid and fuzzy appearing envelope are indicated with black arrowheads (C and D). Each panel has indicated scale bar. Cyt is cytoplasm.