Introduction to Non-Hodgkin's Lymphoma

The Lymphatic System

The lymphatic system represents the body's primary defense mechanism against invasion by foreign, potentially disease-producing microorganisms such as bacteria, viruses, and fungi. In humans, the lymphatic system includes the following components:

• Lymph Nodes - These are pea-sized nodules that are found throughout the lymphatic system and are especially abundant in the groin, armpits, abdomen, and neck areas. Lymph nodes serve to filter-out dead microorganisms that are destroyed by the body's immune system.

• Lymphatic Vessels - The lymphatic vessels are a series of channels or conduits similar to veins that carry a colorless liquid called lymph that is filtered and collected from the body's organs and tissues. Lymphatic fluid contains a rich supply of specialized white blood cells called lymphocytes that are the key cells of the body's immune system.

• Lymphocytes - There are two major types of lymphocytes known as B-lymphoyctes and T-lymphocytes. B-lymphocytes are produced in the bone marrow and regulate or control the production of antibodies - specialized proteins that bind to the surface of microorganisms and facilitate their destruction by other specialized cells of the body's immune system. This type of immunity is called humoral immunity or antibody-mediated immunity because antibodies that are produced by B-lymphocytes are the key cells involved in fighting off the invading microorganisms. There are five major types of antibodies, also called immunoglobulins, produced by B-lymphocytes: IgG, IgM, IgA, IgD, and IgE.

T-lymphocytes are specialized white blood cells that are produced in the bone marrow and mature in the thymus gland, a small gland located in the chest just below the sternum (breastbone). T-lymphocytes are responsible for a type of immunity called cell-mediated immunity. This type of immunity plays an important role in:

• Destruction of the body's cells that have been infected by bacteria, viruses, or fungi

• Destruction of altered (mutated) cells that arise during the course of normal cell division in the body that can potentially turn into cancer cells

Other Components of the Lymphatic System

Other organs of the body that contain lymphatic tissue include:

• Spleen - The large oval-shaped organ on the left side of the body between the stomach and diaphragm that stores red blood cells and white blood cells that are involved in immune responses.

• Thymus gland - A small gland located in the chest just below the breastbone that is involved in the maturation of T-lymphocytes.

• Bone marrow - The soft innermost portion of bone that produces red and white blood cells.

• Tonsils - These are lymphoid organs located at the back of the throat that help the body defend itself against upper respiratory tract infections.

• Adenoids - These are two groups of lymphoid tissue that lie on either side of and at the very back of the throat. In children, the adenoids are thought to be involved in immune responses to infection but, as a person ages, the adenoids shrink in size until they disappear and are, therefore, not likely to be important in protecting against infection.

Functions of the Lymphatic System

The three primary functions of the lymphatic system include:

• Host Defense and Immunity - protecting the body from invasion by foreign organisms

• Maintaining fluid balance in the body by filtering and collecting fluids and proteins from the lymph and returning it back into the bloodstream.

• Absorbing lipids (fats) from the gut and transporting it to the bloodstream.