Phagocytes of humans and other animals are called professional or non-professional, depending on how good they are at phagocytosis. The professional phagocytes are neutrophils, monocytes, macrophages, dendritic cells, and mast cells. The reason they are called professional phagocytes is because they have receptors on their surfaces which can detect harmful objects, such as bacteria. Phagocytes are very important in fighting infections and in getting rid of dead and dying cells.