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Mast cells in cell culture. Mast cells (mastocytes) are cells of the immune system and represent an important link between the innate and acquired immune response.They arise from precursor cells in the bone marrow and migrate as immature cells to many tissues, especially those in close contact with the outside world, where they differentiate.
In the thymus they undergo a process of maturation, which involves ensuring the cells react against antigens ("positive selection"), but that they do not react against antigens found on body tissue ("negative selection"). [11] Once mature, T cells emigrate from the thymus to provide vital functions in the immune system. [11] [12]
The supposition that the role of the thymus might involve a hormone-like mechanism led to the isolation from thymus tissue of a biologically active preparation. Known as "Thymosin Fraction 5", this was able to restore some aspects of immune function in animals lacking thymus gland.
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 ...
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.
TECs, as a component of the thymus, play a key role in thymocyte development and self-tolerance, so their dysfunction causes many autoimmune diseases, tumors of immunodeficiencies. Most frequently are occurred epithelial tumors established from TEC and thymocytes - thymomas and thymic carcinoma.
Major function of cTECs is to positively select those T cells that are capable to recognize and interact with MHC molecules on their surface [3]. Once T cell precursors enter the thymic cortex, they start their transformation from double negative stages (T cell without surface expression of CD4 and CD8 co-receptors) to a double positive stage (T cell with surface expression of both co ...
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]