Macrophages (Greek: big eaters) are cells originating from monocytes, a type of white blood cell found in the body. Macrophages function in both non-specific defense (innate immunity) as well as help initiate specific defense mechanisms (adaptive immunity) of vertebrate animals.
Their role is to phagocytize (engulf and then digest) cellular debris and pathogens, either as stationary or as mobile cells. They also stimulate lymphocytes and other immune cells to respond to pathogens. They are specialized phagocytic cells that attack foreign substances, infectious microbes and cancer cells through destruction and ingestion.
A macrophage of a mouse stretching its “arms” (pseudopodia) to engulf two particles, possibly pathogens.