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Abnormalities of the thymus can result in a decreased number of T cells and autoimmune diseases such as autoimmune polyendocrine syndrome type 1 and myasthenia gravis. These are often associated with cancer of the tissue of the thymus, called thymoma , or tissues arising from immature lymphocytes such as T cells, called lymphoma .
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.
AIRE is a transcription factor expressed in the medulla [broken anchor] (inner part) of the thymus. It is part of the mechanism which eliminates self-reactive T cells that would cause autoimmune disease. It exposes T cells to normal, healthy proteins from all parts of the body, and T cells that react to those proteins are destroyed.
The thymus is where the T lymphocytes mature and become immunocompetent. The loss or lack of the thymus results in severe immunodeficiency and subsequent high susceptibility to infection. In most species, the thymus consists of lobules divided by septa which are made up of epithelium which is often considered an epithelial organ.
Autoimmune disease is a frequent complication after thymus transplantation, found in 42% of subjects over 1 year post-transplantation. [15] However, this is partially explained by that the indication itself, that is, complete DiGeorge syndrome (absence of thymus), increases the risk of autoimmune disease. [16]
Thymoma is a common neoplasm arising from the thymus, the primary lymphoid organ where T cells become educated to distinguish "self" from "non self". In the setting of thymoma, abnormal thymic education occurs as a result of subtle differences in antigen processing. In TAMA these differences result in autoreactive T cells escaping from the thymus.
A 2022 statement from the World Health Organization (WHO), defines the term this way: “Disease X is [used] to indicate an unknown pathogen that could cause a serious international epidemic.”
Thymic hypoplasia is a condition where the thymus is underdeveloped or involuted. Causes