The body's innate immune system is its first line of defense against invaders. A disease-causing bacterium or a piece of wood from a splinter are treated the same: Cellular agents of the immune system identify these objects as foreign and try to destroy them.
Macrophages — literally, 'big eaters' — are a main part of this response. These cells find and engulf invaders, or form a wall around the foreign object. Unfortunately, macrophages also eat helpful foreigners, including nanoparticles that deliver drugs or help image tumors.
Video by Kurtis Sensenig, University Communications