Lymphocyte

• a type of white blood corpuscle with a rounded or kidney-shaped nucleus
  Source: Noland, George B. 1983. General Biology, 11th Edition. St. Louis, MO. C. V. Mosby
• white blood cells that are members of the immune system
  Source: Jenkins, John B. 1990. Human Genetics, 2nd Edition. New York: Harper & Row
• A lymphocyte is a type of white blood cell that is part of the immune system. There are two main types of lymphocytes: B cells and T cells. The B cells produce antibodies that are used to attack invading bacteria, viruses, and toxins. The T cells destroy the body's own cells that have themselves been taken over by viruses or become cancerous.