Immune system

Key facts The immune system defends the body from infection and includes a complex network of cells, chemicals, tissues and organs. The immune system recognises ‘invaders’ such as bacteria, viruses and fungi as well as abnormal cells like cancer cells, and then helps the body fight the invasion. The immune system includes the skin, bone marrow, the thymus, lymphatic system, lymph nodes, the spleen and mucous membranes. There are many different immune conditions, sometimes related to underactivity or overactivity of the immune system. What is the immune system? The immune system defends the body from infection. It contains a complex