Macrophages

Macrophages (Greek meaning 'big eater') are the largest type of white blood cell and, as such, play a key role in immune response.

Macrophages start life as monocytes produced by stem cells in bone marrow. If activated by cytokines, inflammatory messenger models produced by T cells, monocytes differentiate into macrophages . Some of these are then used to carry out phagocytosis on invading pathogens, a form of non-specific immunity while others are used to remove dead/necrotic cells from the host. The macrophages then pull apart the proteins of pathogens to present them on their surface membrane, alerting the immune system to the infection and allowing T cells to carry out their function. Macrophages also produce toxic chemicals to kill surrounding cells and thus preventing pathogenic reproduction.