Phagocytosis. Coloured scanning electron micrograph of a macrophage cell engulfing the bacteria Mycobacterium tuberculosis, a process known as phagocytosis. These bacteria (green) are the cause of tuberculosis (TB) in humans. The macrophage cell (yellow) is a scavenger immune cell found at sites of infection in the body. It removes bacteria or other foreign bodies from blood or tissues, taking on a protective role. M. tuberculosis bacteria are spread by coughing or sneezing, then inhaled into the lungs to form an infected lesion. It causes pulmonary tuberculosis (consumption) which can be fatal. Magnification x1,940 at 6x7cm size.