Many people couldn’t say where their thymus is, or what it does, and even doctors have long considered it expendable in adults. But new Harvard-led research suggests that the walnut-sized organ in the chest actually plays a vital role in immune health as we age, particularly in cancer prevention.
The study comparing data from patients who had their thymus removed with those who had not found that 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.
“The magnitude of risk was something we would have never expected,” said David Scadden, the Gerald and Darlene Jordan Professor of Medicine and professor in the Department of Stem Cell and Regenerative Biology, who led the study published in The New England Journal of Medicine in collaboration with researchers at Massachusetts General Hospital.
“The primary reason why the thymus has an impact on overall health seems to be as a way to protect against the development of cancer.”
The thymus is the fastest-aging organ, according to Scadden. Most active in churning out T-cells during early childhood, it begins to atrophy into fatty tissue around puberty. That’s why, for many decades, scientists assumed it served a limited purpose in adulthood. It is typically removed due to issues with the organ itself, such as thymus cancer, or during other cardiothoracic surgeries because it’s located in front of the heart and is often in the surgeon’s way.
Yet in recent years scientists had started to suspect that the thymus plays an outsize role in our health as we age, by continuing to make T-cells that contribute to the diversity of the body’s overall T-cell population.
“This study demonstrates just how vital the thymus is to maintaining adult health,” Scadden said.