macrophage

A type of white blood cell that helps fight infection by surrounding and killing foreign cells or micro-organisms, removing dead cells and stimulating other immune system cells. 

Macrophages develop from monocytes that have moved from the blood into tissues.

Macrophages are a type of phagocyte (a white blood cell that surrounds and kills bacteria or micro-organisms, eats foreign material, removes old or damaged cells and helps to boost the immune system).