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The primary (or central) lymphoid organs, including the thymus, bone marrow, fetal liver and yolk sac, are responsible for generating lymphocytes from immature progenitor cells in the absence of antigens. [12] The thymus and the bone marrow constitute the primary lymphoid organs involved in the production and early clonal selection of ...
The thymus (pl.: thymuses or thymi) is a specialized primary lymphoid organ of the immune system.Within the thymus, thymus cell lymphocytes or T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders.
Various bird organs function to differentiate avian immune cells: the thymus, Bursa of Fabricius and bone marrow are primary avian lymphoid organs whereas the spleen, mucosal associated lymphoid tissues (MALT), germinal centers, and diffuse lymphoid tissues are secondary lymphoid organs. As a general rule, birds do not have lymph nodes.
In the lymphatic system, a lymph node is a secondary lymphoid organ. [5] Diagram of a lymph node showing lymphocytes. The primary function of lymph nodes is the filtering of lymph to identify and fight infection. In order to do this, lymph nodes contain lymphocytes, a type of white blood cell, which includes B cells and T cells.
They have a pivotal role in primary and secondary lymphoid tissue organisation and in adult lymphoid tissue, regulating the adaptive immune response and maintaining secondary lymphoid tissue structures. [25] Their production is stimulated by retinoic acid, CXCL13, RANK-L, and the cytokines IL-1B, IL-23, and IL-6. [26]
If tissue fluid builds up the tissue will swell; this is called edema. As the circular path through the body's system continues, the fluid is then transported to progressively larger lymphatic vessels culminating in the right lymphatic duct (for lymph from the right upper body) and the thoracic duct (for the rest of the body); both ducts drain ...
In humans, HEVs are found in all secondary lymphoid organs (with the exception of spleen, where blood exits through open arterioles and enters the red pulp), including hundreds of lymph nodes dispersed in the body, tonsils and adenoids in the pharynx, Peyer's patches (PIs) in the small intestine, appendix, and small aggregates of lymphoid ...
Follicular dendritic cells (FDC) are cells of the immune system found in primary and secondary lymph follicles (lymph nodes) of the B cell areas of the lymphoid tissue. [1] [2] [3] Unlike dendritic cells (DC), FDCs are not derived from the bone-marrow hematopoietic stem cell, but are of mesenchymal origin. [4]