How are invading germs destroyed?
Special T-lymphocytes attach themselves to any invading organisms and destroy them. The T-lymphocytes release special substances that attract another type of white blood cell which consumes the invaders. B-lymphocytes are also stored in the lymph system. They release a flow of substances called antibodies. These lock on to invading organisms. Each antibody attacks a particular type of invader, clumping them together so they are destroyed by the white blood cells. When a new infection is found, the B-lymphocytes make an antibody to attack it.
Can our bodies attack themselves?
Sometimes the immune system mistakes some harmless material for an invader and this can cause illness.
Grass pollen and dust are harmless materials that are often inhaled. In some people the body mounts a fierce attack on them. The immune system releases the substances normally designed to fight infection, and their effects can cause illnesses such as hay fever and asthma. Sometimes the immune system attacks normal tissue or organs, causing a condition called auto-immune disease. This can produce serious illness, but fortunately it is quite rare.
Why can the body reject a transplant organ?
All your body cells carry a ‘label’, or marker substance, on the outside of the cell. This marker is recognized by the immune system, which will not attack it. In some very serious illnesses, when a person’s organ has failed completely, an organ from another individual may be transplanted. The donated organs carry different marker substances, so the immune system treats them as invaders and will mount an attack on them called rejection. These attacks from the immune system can be reduced or prevented by the use of powerful drugs.
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