Phagocytosis (literally "cell-eating") is a form of endocytosis wherein large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a phagosome, or "food vacuole."
In animals, phagocytosis is performed by specialized cells called phagocytes, which serve to remove foreign bodies and thus fight infection. In vertebrates, these include larger macrophages and smaller granulocytes, types of blood cells. Bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytosed. Virulent bacteria may need to be coated in antibodies before they can be consumed. Certain pathogenic bacteria, such as those of leprosy and tuberculosis, once internalized by phagocytosis, are resistant to killing by the phagocytes that have ingested them. Anything that impedes or prevents the action of phagocyctes is termed antiphagocytic.
A great body of evidence continues to mount showing that resident, neighbouring cells in a tissue will phagocytize their apoptotic neighbours, thus maintaining tissue homeostasis. This clearance can, depending on the location, facilitate greater clearance than that achieved by resident macrophages.
The most important facet of phagocytosis is its control of inflammation. Depending on the phagocytosed particle, phagocytosis can induce inflammation or, as is the case with apoptotic cells, induce resolution of inflammation. Phagocytosis is also involved in immune tolerance, which prevents inflammation against normal components of the body.