Summary Information: Phagocytic Cells. Phagocytic Cells: Phagocytic cells are white blood cells and other types of cells that are a part of the immune system. Phagocytic cells have the ability to surround and destroy foreign substances in the body. This action, called phagocytosis, plays an important role in defending the body against harmful substances, such as bacteria, viruses, foreign bodies, and other micro-organisms that can cause diseases and abnormal conditions.