What is the thymus (organ)?
The thymus is an organ found in children and other young mammals between the breastbone (sternum) and windpipe (trachea) in the anterior mediastinum. It is highly developed in children, but shrinks after puberty.
For a long time it was thought that the thymus is an (almost) useless organ. Only since one is to experiment with the removal of the thymus gland (thymectomy =) we got an idea of the function of thymus. The thymus gland is one of the most important organs in our immune system. An important part of the lymphocytes, the so-called "T-lymphocyte" (T of Thymus) are "mature". In addition, the thymus plays a vital role in the production of "memory cells" that remember the recipe how the antibodies should be created against experienced diseases.
If the thymus in young animals is removed, occurred in these animals then the following symptoms:
- weight loss
- to slow growth
- hair Loss
- general decline in health status
- many infections, in particular as a consequence of intracellular micro-organisms
- reduced rejection - eventuele- grafts
These phenomena do not occur if the thymectomy is performed in older animals. The phenomena can be prevented or reversed by the after thymectomy to place a piece of thymic tissue back into the body.
In a (human) baby which during embryonic development thymus was not arise, the following phenomena were observed:
- many infections
- no increase in secondary lymphoid organs (including liver and spleen) during infections; the places where normal T lymphocytes there were empty
- slightly reduced concentration of antibodies in the body fluids
- no T-lymphocytes in the blood
These and other observations that one has obtained during these experiments have led to the formulation of the following thymus function:
- the thymus allows for the development of lymphocytes to T-lymphocytes, which are sensitive to a particular antigen.
- the thymus allows for the elimination of T-lymphocytes, which fit on the body epitopes (= self-reactive clones)
- thymus produces hormones (including thymosin) that stimulate the growth and the immune system.