Macrophages are a type of the White Blood Cells that is a part of the immune system of the body. Macrophages are the first line of defence. They engulf the foreign bodies, foreign particles, cancerous cells and infected cells. They do it by searching for a protein marker on the surface of these foreign bodies. When the marker is absent they attack these bodies by performing phagocytosis.
Langerhans cells present on the skin are specialised macrophages that form the first line of defence.