Researchers at Aarhus University are reshaping our understanding of the immune system: a small organ, long believed to cease functioning early in adult life, plays a lifelong role in the risk of cancer and cardiovascular disease – and in determining whether modern cancer treatments are effective.
Aarhus, Denmark 19 March 2026
The small organ in question is the thymus, located behind the breastbone, which is now set to assume a new and more prominent place in textbooks on the immune system, cancer therapies and the risk of cardiovascular disease.
The thymus is where our T cells – the immune system’s most formidable soldiers in the fight against disease – mature. The organ gradually shrinks, and until now it was widely believed that it stopped functioning entirely in early adulthood, meaning that no new T cells were produced thereafter. However, two new studies from Aarhus University now overturn that thesis, explains Nicolai Birkbak, Professor at the Department of Clinical Medicine, Aarhus University, and Department of Molecular Medicine, Aarhus University Hospital, and one of the researchers behind the two studies, which have just been published in the scientific journal Nature :
“This is significant and potentially paradigm-shifting new knowledge. It challenges the prevailing view that the thymus has no importance in adult life. On the contrary, our studies show that a healthy thymus may be crucial both for disease risk and for how well you respond to cancer treatments,” he explains.
In one of the two studies, the researchers examined the importance of the thymus in cancer patients treated with immunotherapy. Immunotherapy works by activating the patient’s own T cells to recognise and attack cancer cells in the body. According to Nicolai Birkbak, the study shows that the healthier the thymus, the better patients respond to treatment.
“Our study shows a marked difference in how patients respond to immunotherapy – those with well-preserved thymus function respond better and live longer.”
This may have implications for how patients are treated in the future, he believes.
“Our studies show that it is important to consider the patient’s overall immunological status, and not focus solely on the tumour, when deciding which treatments to offer.”
The good – and perhaps bad – news is that your lifestyle helps determine how quickly your thymus shrinks and therefore how many new T cells it can mature. If it shrinks rapidly, this may have serious consequences for your health, says Nicolai Birkbak.
“Our studies show significant differences in the rate at which the thymus shrinks – both between sexes, but especially in relation to lifestyle factors such as smoking, obesity and low levels of physical activity. A thymus with low function is associated with an increased risk of early death and of developing cancer or cardiovascular disease.”
However, the new insight into the importance of the thymus may also pave the way for entirely new approaches to prevention, he adds.
“It opens new perspectives. In the long term, it may become relevant to identify individuals with rapid thymus decline and investigate whether it is possible to slow or influence the process, thereby reducing the risk of developing serious diseases such as cardiovascular disease or cancer. This could potentially improve their ability to receive treatment if they are affected.”
Together with the rest of the research group, he hopes the findings will pave the way for more and better research into how the immune system varies and what this means for our health and treatment options.
Professor Nicolai Juul Birkbak
Department of Clinical Medicine, Health, Aarhus University
Phone: +4578455347
Mail: nbirkbak@clin.au.dk
Nature
Observational study
People
Thymic health consequences in adults
18-Mar-2026
No conflicts of interest