A macrophage is a cell that is known as a phagocyte. This type of cell is part of the defense system known as the immune response. It can engulf and then digest cellular debris as well as pathogens. Their presence stimulates the lymphocytes--white blood cells which are part of the innate immune system. These help to defend the host from tumors and viruses. Macrophages ingest pathogens by phagocytosis(surrounding and engulfing the invader). Then, a phagosome is formed. When a lysosome, an organelle in the cell with enzymes, fuses with the phagosome, a phagolysosome forms. Inside, the pathogen is digested by enzyme action. Wastes are assimilated or sent out through the cell membrane. If there was a wound but no macrophages, healing would be delayed due to the fact that cellular debris would not be able to be broken down and disposed of properly.