Thymus longevity research points to immune role in aging
Studies tie a healthier thymus to longer life and lower disease risk, but researchers say causation and safe treatments remain unproven.
By James Whitfield · Staff Writer
4 min read
Thymus longevity research is drawing new attention to a small gland in the upper chest that helps train the immune system. Researchers cited by Al Jazeera say recent studies link a healthier thymus with longer survival and lower rates of cancer and cardiovascular disease, though they have not proved the organ causes those outcomes.
The thymus sits behind the breastbone and in front of the heart. According to Paola Bonfanti, a professor at University College London’s Institute of Immunity and Transplantation, it is large and active early in life, then begins shrinking in childhood and loses more function after puberty.
What is the thymus?
The thymus is the place where immature immune cells become T cells, a type of white blood cell that can attack infected or cancerous cells and help direct immune defenses. Bonfanti told Al Jazeera that as the gland shrinks, its output of newly made T cells falls, a change that can be measured in blood.
Doctors long gave the thymus little attention because it was thought to become inactive after puberty, Al Jazeera reported. Bonfanti said the organ does not vanish in older adults; instead, much of its working tissue is replaced over time by fat and connective tissue, while some functional tissue can remain.
What did recent thymus studies find?
In March, Harvard Medical School-led researchers published a study in Nature that used artificial intelligence to review thousands of CT scans, according to Al Jazeera. The team found that adults whose thymus looked healthier on scans lived longer and had lower rates of cardiovascular disease and cancer than adults whose thymus appeared unhealthy.
A second Nature study in the same edition looked at cancer patients and CT scans, Al Jazeera reported. It found that thymic health may affect how patients respond to immunotherapy, a treatment that depends on the patient’s immune system.
Al Jazeera also cited a 2023 study that compared people who had their thymus removed with people who did not. Five years after removal, the thymus-removal group was three times more likely to die and twice as likely to develop cancer, according to that study.
Bonfanti cautioned that these findings show association, not proof. She said healthier people may be more likely to retain thymus tissue as they age, rather than the larger or healthier thymus being the reason they remain healthier.
Could thymus regeneration slow aging?
Researchers do not yet know whether restoring thymus function would improve immunity or extend life, Al Jazeera reported. Bonfanti said stronger thymic function supports the production of new T cells and a broader T-cell repertoire, which is tied to better immune responses.
She also said age-related decline in thymus activity is associated with reduced vaccine responses, weaker defenses against new infections and slower immune rebuilding after treatments such as bone marrow transplantation. Other parts of the immune system also age, including bone marrow, lymph nodes and immune cells themselves, she said.
Nature reported that the thymus may be able to regenerate in some circumstances. David Scadden, a haematologist at Massachusetts General Hospital in Boston, said the organ can shrink during pregnancy and recover after delivery, according to Al Jazeera’s account of the Nature report.
What comes next for thymus treatments?
Bonfanti said scientists still do not fully understand what makes the thymus shrink with age, which cells are lost first or which signals might stop that process. Those gaps leave open the question of whether treatment aimed at the thymus can be safe and effective.
Nature reported that Tolerance Bio, a biotechnology company in Philadelphia led by Francisco Leon, is developing an antibody intended to slow thymus shrinkage, according to Al Jazeera. The company has not disclosed further details but has said it plans clinical trials next year.
Bonfanti told Al Jazeera that if thymus regeneration works, the earliest patients would probably be people with serious medical need rather than healthy people hoping to slow aging. Researchers still have to show that changing the thymus can improve health outcomes, not only that thymus health tracks with them.
This story draws on original reporting from Al Jazeera.