Removal of the Thymus Illustrates the Importance of Thymic Atrophy in Aging

The thymus is a small organ in the chest. Thymocytes created in the bone marrow migrate to the thymus where they mature into T cells of the adaptive immune system through a complex process of selection. The thymus atrophies with advancing age, and this reduces the pace at which new T cells are generated to reinforce the immune system. Absent reinforcements the adaptive immune system declines into malfunctioning, senescent, exhausted cell populations over time. This immune dysfunction is an important component of degenerative aging. The same harms are demonstrated in adult individuals who had to have their thymus removed, as noted here.

Surgical removal of the thymus is recommended in patients with the autoimmune disease myasthenia gravis as a way to halt T-cell-induced immune destruction of nerve endings. For the study, researchers mined data from 1,146 adult patients who had undergone thymus removal, alongside demographically matched control patients who had undergone similar surgeries but kept their thymus. Thymectomy patients had a nearly threefold higher risk of death from a variety of causes, including a twofold higher risk of cancer and a more modest increase in autoimmune diseases.

In an analysis involving all patients with more than five years of follow-up, the rate of death was higher in the thymectomy group than in the general U.S. population ­- 9 percent vs. 5.2 percent, as was death due to cancer, or 2.3 percent vs. 1.5 percent. In a subgroup of patients in whom T-cell production was measured, those who had had their thymus removed had less new production of T-cells, including both helper T-cells and cytotoxic T-cells. Those patients also had higher levels of pro-inflammatory cytokines, which are small signaling proteins associated with autoimmunity and cancer, in their blood.

The analysis was facilitated by recent advances in rapid genetic sequencing of T-cell receptors (TCRs). The technology, called TCR sequencing, has enough resolution to allow scientists to not only identify different types of T cells, but also measure their diversity as a population overall. "This study demonstrates just how vital the thymus is to maintaining adult health."



Anybody know whether half a thymus is good enough, like as good as one kidney? My mum had a partial thymectomy.

Posted by: Barbara T. at August 10th, 2023 2:57 PM
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