Spleen is the largest organ of adult lymphatic system, located behind the stomach, in the abdominal cavity. It resembles a lymph node, but it is larger than lymph nodes. It is made up of two types of tissues. (1) Red pulp that removes bacteria and lymphocytes (white blood cells) and macrophages. (2) White pulp is mainly lymphocytes. Spleen filters the blood and brings blood into contact with lymphocytes, which destroy harmful substances.
Peyer’s patch is a set of round or oval nodules, mostly found in the lowest portion (ileum) of the small intestine. These nodules of lymphatic cells aggregate and form bundles or patches. These nodules exercise protective function in the intestine. They protect the intestine from bacterial invasion. During the typhoid fever, these are the site of inflammation.