Some lymphocytes, which are white blood cells particularly involved in fighting infection, enter the bloodstream before they are fully mature. They go to a small gland called the thymus, situated below the breastbone, when they mature and develop more infection-fighting qualities. When they leave the thymus gland, they are known as T-lymphocytes or T-cells, after the fact that they have been influenced by the 'T'hymus gland. These T cells have special proteins on their surfaces so that they can deal with cancer and other harmful cells. There are three different types, each with their own responsibility.
The Regulatory T-cells help to keep the immune system under control, so that it doesn't attack healthy cells.
The Helper T-cells help the other T cells do their work.
The Killer T-cells destroy unwanted cells. They recognise them, and deal with them efficiently.
Don't we have an amazing body?
There are exciting developments in this area where doctors are pumping extra Killer T-cells into diseased bodies in an effort to help the immune system conquer the disease.