A macrophage is type of white blood cell whose main function is to destroy and engulf bacteria and foreign microorganism within tissue. That is why it is said that a macrophage is a phagocytic cell, which means it phagocytizes (devours) bacteria, bacteria-infected cells, and debris. Macrophages are also involved in the immune response, as they are activated by cytokines released by T cells lymphocytes; once activated macrophages begin not only to kill and phagocytize foreign bodies, but also to divide and multiply as bigger and stronger macrophages.
Macrophages measure 21 micrometers in diameter. They are produced by the division of monocytes. Another importan function performed by the macrophages is the removal of necrotic cellular debris in the lungs. The removal dead cell material is important in chronic inflammation, as the early stages of inflammation are dominated by neutrophil granulocytes, which are ingested by macrophages when they die.