(a) Tetherin on the cell surface of A3.01 T cells infected with NLUdel virus, treated with indinavir to preserve particle morphology for preparation. Arrows indicate immunogold beads; primary antibody was rabbit anti-tetherin polyclonal antisera. (b) Schematic depiction of parallel homodimers of tetherin retaining HIV particles on the plasma membrane; tetherin is not to scale in this diagram.