A macrophage is a type of white blood cell that plays a crucial role in the immune system. These cells are responsible for detecting, engulfing, and destroying pathogens like bacteria and viruses. They also help remove dead or damaged cells from the body, contributing to tissue repair and maintenance. Macrophages originate from stem cells in the bone marrow and can be found in various tissues throughout the body. They can adapt to different environments and perform specialized functions, such as presenting antigens to T cells, which helps activate the adaptive immune response.