AIDS pneumonia infection. Coloured transmission electron micrograph (TEM) of a section through Pneumocystis carinii protozoa causing pneumonia. The protozoa are crescent-shaped (red/yellow). They are in lung sputum from a patient suffering from acquired immune deficiency syndrome (AIDS). The AIDS virus (HIV, human immunodeficiency virus) destroys lymphocytes in the immune system that normally defend against opportunistic infections like this. Magnification: x6600 at 6x7cm size.