Macrophages. Coloured Scanning Electron Micrograph (SEM) of two macrophages, part of the body's immune response system. These are solitary cells which engulf and devour (by a process known as phagocytosis) invading microorganisms throughout the body. The projections on the surface of each cell help the macrophage to fasten onto its prey. Macrophages are a type of white blood cell which are found outside the bloodstream, mainly in connective tissue. If an infection occurs, by bacteria entering a wound for example, macrophages migrate to the site of infection and ingest the bacteria. Magnification: x1,525 at 6x7cm size. Magnification: x2,440 at 4x5 inch size.