Color enhanced scanning electron micrograph (SEM) of macrophages with projectile-looking surfaces interacting with lymphocytes (rounded). Macrophages are monocytes (white blood cells) that have left the blood and become phagocytic cells. The act as part of the immune system, engulfing foreign material and dying cells in the body. Lymphocytes are white blood cells that function as a part of the immune system. There are different types of lymphocytes, each with a different task. They make antibodies, kill viruses, enhance the production of antibodies, or bring macrophages and neutrophils to sites of infection or tissue damage (inflammatory T cells).