The name macrophage means 'big eater' and aptly describes these, the largest of the white blood cells which form an important part of the body's defences.
Their job is to wander through the bloodstream and tissues of the body engulfing and removing unwanted debris. The debris might be dust, such as house dust, from DIY activities or even talc, pollen etc. we have breathed in to the lungs, it might be bacteria or parasites that have invaded the tissues or it might be damaged and dead cells of the body itself. Once engulfed, the macrophages kill any bacteria and break down the particles of debris and ensure the remnants are removed from the body via the faeces. They are the dustbinmen of the body, are essential for health and can even remember past encounters to help the body respond more efficiently to the same foreign material next time.