Macrophages digest the invading bacteria and viruses with the digestive enzymes found in cellular organelles called

Lysozyme which is found in the lysosomes. They function at a relatively low pH and are so because if they functioned at physiological pH they would digest the cell. But in this case, they are in the lysosomes where they are safe and at a lower pH so when the vesicles open they can emit hydrogen ions and the lysozyme to digest the foreign material.