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Lymphocyte
Lymphocytes are small white blood cells that carry out most of the activities of the immune system. There are about one trillion lymphocytes in the human body. They can be classified into two main types: B cells and T cells (1). Both types are made in the bone marrow, and both must fully mature before they can assist in the immune response. However, B cells remain in the bone marrow to maturity, while immature T cells travel through the blood stream to the thymus gland to complete their development. Once they are fully developed, the B and T cells travel to the spleen and lymph nodes, where they await opportunity to fight infection (2).
The B cells make antibodies that attack bacteria. Antibodies are proteins with two ends; one end sticks to proteins on the outside of white blood cells, and the other end sticks to the infected or damaged cell and helps to destroy it. The antibody produced is often unique for each type of infection. Once the antibody attaches to the surface of the invading bacteria or virus, the invader is labeled so that the next time the infection is encountered, the B cells are able to produce the antibody more quickly (2, 3).
T cells function through the release of proteins known as cytokines, which are able to signal to cells to grow, divide or die, depending on the effect most beneficial to the immune system. There are several types of T cells, but the two main types are killer T cells and helper T cells. Killer T cells directly attack the body's cells that have been infected, preventing the diseased cells from spreading. Helper T cells, on the other hand, direct cellular activity instead of attacking disease directly. Their function includes stimulating the B cells to make antibodies and influencing the activity of the killer T cells
(2, 4).
Because the role of lymphocytes is central to the function of the immune system and the body's ability to combat disease, they are a main focus in the study and treatment of cancer (2).
- "Lymphocytes." From MedicineNet.com. Available: http://www.medterms.com/script/main/art.asp?articlekey=4220 (Accessed August 8, 2007).
- "The Immune System." From Cancer Research UK's website. Available: http://www.cancerhelp.org.uk/help/default.asp?page=118 (Accessed August 8, 2007).
- "Immune System Series: Lymphocytes." From ImmuneCentral.com. Available: http://www.immunecentral.com/immune-system/iss6.cfm (Accessed August 8, 2007).
- Patil, N., Ph.D. (2000) "Immune System: T Cell Immunity." From PersonalMD.com. Available: http://www.personalmd.com/news/tcells_10312000.shtml (Accessed August 8, 2007).