present at birth, continues to grow untill puberty begins, primary lymphoid organ, located in between heart and the breastplate, butterfly in shape MAJOR FUNCTION:directing the maturation of thymocytes to T lymphocytes.
Is a maturation process. T cells that are beneficial to the immune system are spared, while those T cells that might evoke a detrimental autoimmune response are eliminated. The mature T cells are then released into the bloodstream.
present inside the bones, is not actually an organ, but it is essential for the functioning of immune system, considered a primary lymphoid site, immature thymocytes, B cells and other lymphatic cells are originated in the BM, Some of these cells mature in the bone marrow itself, while others are circulated to different parts to undergo maturation. NB ALL OF THE CELLS OF THE IMMUNE SYSTEM ARE INITIALLY DERIVED FROM BM. They form through a process called hematopoiesis. Produces B cells, natural killer cells, granulocytes and immature thymocytes, in addition to red blood cells and platelets
bone marrow-derived stem cells differentiate into either mature cells of the immune system or into precursors of cells that migrate out of the bone marrow to continue their maturation elsewhere.
Bean shaped, found throughou the body, house lymphocytes (T & B), dendritic cells and macrophages, help filter lymph so unwanted particles can be destroyed. NB* The fluids after filtration in the lymph nodes are released back to the bloodstream.
What happens to Ag in the lymph?
they are filtered out of the lymph in the lymph node before returning the lymph to the circulation. (The macrophages and dendritic cells that capture antigens present these foreign materials to T and B cells, consequently initiating an immune response) - ALSO TAKES PLACE IN THE SPLEEN*
On left side of the abdominal cavity, is a secondary lymphoid organ, contains many T-cells(detect the presence of antigens during blood circulation). Functions include filtering the blood to destroying the unused blood cells. B cells become activated (CD4 or T Helper 2 cells acticate B Cells to secrete immunoglobulin,Ig) and produce large amounts of antibody(Ig). Also, old red blood cells are destroyed in the spleen.
Mucosal Associated Lymphoid Tissues or MALT
is the diffusion system of small concentrations of lymphoid tissue found in various sites of the body, such as the gastrointestinal tract, thyroid, breast, lung, salivary glands, eye, and skin. Is a secondary lymphoid organ, containing plasma cells that produce antibodies, T & B cells, macrophages. MALT plays a role in regulating mucosal immunity, defending against the microbes making their way through the mucous lining. It may be the site of lymphoma.
Cutaneous Associated Lymphoid Tissues (CALT)
Another tertiary lymphoid organ is the skin. It is a basic part of immune system, which acts as a barrier to prevent foreign particles from entering inside the host. The large surface area of the skin is effective in providing nonspecific defenses (innate) to the host body.