The thymus is largest and most active during the neonatal and pre-adolescent periods. By the early teens, the thymus begins to decrease in size and activity and the tissue of the thymus is gradually replaced by fatty tissue. Nevertheless, some T cell development continues throughout adult life.
Full Answer
Jun 08, 2009 · The thymus produces and secretes thymosin, a hormone necessary for T cell development and production. The thymus is special in that, unlike most organs, it is at its largest in children. Once you reach puberty, the thymus starts to slowly shrink and become replaced by fat. By age 75, the thymus is little more than fatty tissue.
Mar 21, 2022 · the thymus undergoes a process known as involution, which is defined as a decrease in the size, weight and activity of the gland with advancing age. Thymic involution is thought to result from high levels of circulating sex
We now know that the thymus receives percursors of T cells, called thymocytes, from the bone marrow and helps them to mature into full-fledged T cells (such as CD4 or CD8 cells) that are trained to attack foreign cells. NIH researchers have played a key role in moving the field of thymus research forward. Transforming the field
Feb 28, 2020 · Its main function is to support the maturation of T cells, which are essential white blood cells and part of the adaptive immune system that protects us from infections and tumor cells. Up to now,...
As we age, the thymus increasingly turns into a mass of fat cells; this new research could help to explain why. The research team has identified a stromal progenitor, a type of cell that can transform into several other types of cells, and in the thymus, stromal progenitors readily change into fat cells.Jan 5, 2018
First of all, it is important to underline that the human thymus develops during fetal life, reaches its maximal output during early postnatal life, and declines in size and output during young adulthood and throughout adult life through the process of age-related involution (Chinn et al. 2012).
Consequences of Thymus Removal The thymus gland is important because it trains the immune system to fight infections. Much of this training occurs before birth. However, studies have linked removing the thymus in infants to an increased risk of infections and autoimmune disorders.Oct 22, 2021
Summary: A critical immune organ called the thymus shrinks rapidly with age, putting older individuals at greater risk for life-threatening infections. A new study reveals that thymus atrophy may stem from a decline in its ability to protect against DNA damage from free radicals.Aug 6, 2015
It wasn’t until the early 1960s that Australian immunologist Jacques Miller made an amazing discovery: The thymus is the place where T cells, the major effector cells of the immune system, are generated. This image of a mouse thymus shows all cells in the thymus (blue); the red portion indicates the thymus medulla.
Thymocytes, the precursor of T cells, develop in a region of the thymus called the thymic cortex; selected thymocytes proceed to the thymic medulla and become mature T cells; and eventually the T cells are released into the bloodstream. Yousuke Takahama (Tokushima University in Tokushima, Japan) described how the protein C-C motif chemokine receptor type 7 (CCR7) is essential for the cortex-to-medulla migration and for establishing self-tolerance, thereby preventing tissue-specific autoimmunity. Consequently, he found that in mice, the deletion of CCR7’s binding partners–C-C motif ligands 21A and 19—had a negative effect on establishing immune tolerance.
In 2000, Alfred Singer ’s group at the National Cancer Institute (NCI) transformed the field of thymus biology by demonstrating a novel selection mechanism for thymocyte lineage choice and maturation, called the “kinetic signaling” model (Immunity 13:59–71, 2000). A major revelation of this study was that lineage fate decisions are made by the “kinetics,” and not the “strength,” of the T-cell receptor signaling as previously thought. This seminal finding was highlighted in 2016 in the Journal of Immunology as a “Pillar of Immunology” article for its countless citations, for changing the conventional view on thymocyte selection and maturation, and for advancing thymus research ( J Immunol 196: 1985–1997, 2016 ).
Paul Love’s lab focuses on mammalian hematopoiesis and has a long history of studying the process of T-cell development, which begins when multipotent progenitor cells, derived from hematopoietic stem cells in the bone marrow, migrate to the thymus. In 2009, his lab identified thymocyte-expressed molecule (THEMIS), a signaling protein that is critical in lymphocyte maturation and controls the fate of lymphocytes (Nat Immun 10:840–847, 2009) [ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2848698/]. Love is particularly interested in investigating signal-transduction molecules and pathways that regulate T-cell maturation in the thymus. THEMIS—named for the Greek Titaness who advised the chief god, Zeus, on the rules of fate—is involved in lymphocyte maturation and controls the fate of lymphocytes as they differentiate. The Love lab is continuing to study the intricate details of signaling pathways in lymphocyte maturation and the role of THEMIS.
The thymus is one of the most important organs in the body, and it is where thymocytes produced in the bone marrow travel to become new T cells before being trained in the lymph nodes to become the defenders of the adaptive immune system. However, as we get older, the thymus increasingly turns to fat and starts to shrink, causing its ability to produce new T cells to fall dramatically. This process is known as thymic involution and actually begins shortly after puberty, so this is one aspect of aging that begins fairly early in life, although it is many decades later before its decline causes serious health issues.
The researchers show that BMP4 and activin are growth and differentiation factors that are key to the self-renewal and differentiation of thymic epithelial stem cells and that a change in their levels due to aging causes the loss of these epithelial cells.