Search results
Results from the WOW.Com Content Network
Hassall's corpuscles (also known as thymic bodies) are structures found in the medulla of the human thymus, formed from eosinophilic type VI thymic epithelial cells arranged concentrically. These concentric corpuscles are composed of a central mass, consisting of one or more granular cells, and of a capsule formed of epithelioid cells.
The thymus (pl.: thymuses or thymi) is a specialized primary lymphoid organ of the immune system. ... Micrograph showing a Hassall's corpuscle, found within the ...
In 1989, two scientific groups came up with the hypothesis that the thymus expresses genes which are in the periphery, strictly expressed by specific tissues (e.g.: Insulin produced by β cells of the pancreas) to subsequently present these so-called "tissue-restricted antigens" (TRAs) from almost all parts of the body to developing T cells in order to test which TCRs recognize self-tissues ...
Histology of the thymus showing the cortex and medulla Minute structure of thymus. The ability of T cells to recognize foreign antigens is mediated by the T cell receptor (TCR), which is a surface protein able to recognize short protein sequences ( peptides ) that are presented on MHC .
The blood–thymus barrier regulates exchange of substances between the circulatory system and thymus, providing a sequestered environment for immature T cells to develop. The barrier also prevents the immature T cells from contacting foreign antigens (since contact with antigens at this stage will cause the T cells to die by apoptosis ).
Since its discovery in 2001, [3] AIRE (Autoimmune regulator) has been the main focus of studies of thymic (central) immune tolerance.AIRE induces the expression of many antigens specific to differentiated cells not found in the thymus (termed peripheral tissue antigens or tissue restricted antigens) thus helping to detect and remove T cells that react with these antigens. [4]
Periarteriolar lymphoid sheaths (or periarterial lymphatic sheaths, or PALS) are a portion of the white pulp of the spleen.They are populated largely by T cells and surround central arteries within the spleen; the PALS T-cells are presented with blood borne antigens via myeloid dendritic cells.
Thymic involution is the shrinking of the thymus with age, resulting in changes in the architecture of the thymus and a decrease in tissue mass. [1] Thymus involution is one of the major characteristics of vertebrate immunology, and occurs in almost all vertebrates, from birds, teleosts, amphibians to reptiles, though the thymi of a few species of sharks are known not to involute.