Lymphatic system: Encyclopedia II - Lymphatic system - Secondary lymphoid organs

Lymphatic system - Secondary lymphoid organs

The spleen, lymph nodes, and accessory lymphoid tissue are the secondary lymphoid organs. These organs contain a scaffolding that support circulating B- and T-lymphocytes and other immune cells like macrophages and dendritic cells. When micro-organisms invade the body or the body encounters other antigens (such as pollen), the antigens are transported from the tissue to the lymph. The lymph is carried in the lymph vessels to regional lymph nodes. In the lymph nodes, the macrophages and dendritic cells phagocytose the antigens, process them, and present the antigens to lymphocytes, which can then start producing antibodies or serve as memory cells to recognize the antigens again in the future.

The spleen contains lymphocytes that filter the blood stream rather than the lymphatics. Thus, the spleen has importance in fighting infections that have invaded the blood.

Mucosa-associated lymphoid tissue is specialised lymphoid tissue associated with the mucosa of a number of organs.

Adapted from the Wikipedia article "Secondary lymphoid organs", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki