Describe how phagocytosis of a virus leads to presentation of its antigens

Firstly, specialised white blood cells, known as macrophages, detect the virus in the blood stream. This is due to the virus releasing chemicals, and in the process of chemotaxis, the macrophage follows this chemical gradient to the virus. When the macrophage meets the virus, cell surface receptors on the macrophage bind to the virus' antigens. This causes the macrophage to engulf the virus particle, forming a "bubble-like" structure around the virus known as a phagosome. A lysosome then fuses to the phagosome, forming a phagolysosome. Lysosomes contain lysozymes, which are hydrolytic enzymes, and these digest the virus particle. The antigens from this virus particle are then presented on the surface of the macrophage.