HIV infected macrophage. Coloured ion-abrasion scanning electron micrograph (IA-SEM) of a macrophage white blood cell infected with human immunodeficiency virus (HIV, red). A transmission electron micrograph (TEM) slice through the cell is also seen (lower left). HIV infects the immune system's T-lymphocytes, ultimately killing them, leading to a very weak immune system. IA-SEMs allow nanoscale three dimensional imaging of whole cells.