ALFRED PASIEKA / SCIENCE PHOTO LIBRARY ALFRED PASIEKA / SCIENCE PHOTO LIBRARY
T-lymphocyte. Computer graphic image of a T- lymphocyte, also known as a T-cell. T-cells are white blood cells which play an important role in the human immune system. They are divided into three main groups: killer cells, helper and suppressor cells. Killer cells are stimulated by the presence of foreign bodies such as viruses; they travel and attach to these foreign cells destroying them by releasing chemicals known as lymphokines. Helper cells enhance the activities of the killer T-cells whereas suppressor T-cells have the effect of switching off the immune system.
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