HIV infected T-cell. Colored Scanning Electron Micrograph (SEM) of a T-lymphocyte white blood cell infected with Human Immunodeficiency virus (HIV). HIV is the virus causing AIDS (Acquired Immune Deficiency Syndrome). The cell (green) has a folded surface often with projections; small viruses (pink dots) can be seen budding from the cell. HIV infects T-cells, a type of cell involved in the body's immune response, and it instructs the cell to produce more HIV viruses. By this process of infection the virus reproduces and the T-cell is weakened and finally dies. Depletion of T-cells weakens a person's immune system in AIDS.