Researchers at Aarhus University are challenging long-standing assumptions about the immune system. Their findings suggest that a small organ, once thought to stop working early in adulthood, continues to influence cancer risk, cardiovascular disease, and how well patients respond to modern cancer therapies.

That organ is the thymus, located behind the breastbone. It may now take on a more prominent role in how scientists understand immunity, cancer treatment, and heart disease risk.

The thymus is responsible for maturing T cells, which are essential for fighting infections and disease. It gradually shrinks with age, and scientists have long believed it becomes inactive in early adulthood, producing no new T cells after that point. However, two new studies from Aarhus University, published in Nature, challenge that idea.

Nicolai Birkbak, a professor at the Department of Clinical Medicine at Aarhus University and the Department of Molecular Medicine at Aarhus University Hospital, and one of the researchers behind the studies, explains: “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.”