Claim: Lymph nodes are major sites of cells of the immune system.

A lymph node or lymph gland , is an ovoid or kidney-shaped organ of the lymphatic system , and of the adaptive immune system , that is widely present throughout the body . They are linked by the lymphatic vessels as a part of the circulatory system . Lymph nodes are major sites of B and T lymphocytes , and other white blood cells . Lymph nodes are important for the proper functioning of the immune system , acting as filters for foreign particles and cancer cells . Lymph nodes do not have a detoxification function , which is primarily dealt with by the liver and kidneys .   In the lymphatic system the lymph node is a secondary lymphoid organ . A lymph node is enclosed in a fibrous capsule and is made up of an outer cortex and an inner medulla .   Lymph nodes also have clinical significance . They become inflamed or enlarged in various diseases which may range from trivial throat infections , to life-threatening cancers . The condition of the lymph nodes is very important in cancer staging , which decides the treatment to be used , and determines the prognosis . When swollen , inflamed or enlarged , lymph nodes can be hard , firm or tender .