A new study published in the New England Journal of Medicine has found evidence that the thymus is important for adult health in general, as well as for preventing cancer and possibly autoimmune disease.

The thymus gland, which produces immune T cells before birth and during childhood, is frequently thought to be nonfunctional in adults, and it is sometimes removed during cardiac surgery to allow easier access to the heart and major blood vessels.

To see if the thymus benefits adults' health, the researchers compared the risk of death, cancer, and c in 1,146 adults who had their thymus removed during surgery to 1,146 demographically matched patients who underwent similar cardiothoracic surgery without thymectomy.

T-cell production and blood levels of immune-related molecules were also measured in a subset of patients by the researchers.

“By studying people who had their thymus removed, we discovered that the thymus is absolutely required for health. If it isn’t there, people’s risk of dying and risk of cancer is at least double,” said senior author David T. Scadden, MD, director of the Center for Regenerative Medicine at MGH and co-director of the Harvard Stem Cell Institute.

“This indicates that the consequences of thymus removal should be carefully considered when contemplating thymectomy.”

An additional analysis involving all thymectomy patients with more than five years of follow-up found that the overall mortality rate was higher in the thymectomy group than in the general U.S. population as was cancer mortality.

Although Scadden and his colleagues discovered that the risk of autoimmune disease did not differ significantly between the thymectomy and control groups overall in their study, they did notice a difference when patients with infection, cancer, or autoimmune disease prior to surgery were excluded from the analysis.

T cell production and immune-related molecules were measured in a subset of patients (22 in the thymectomy group and 19 in the control group, with an average follow-up of 14.2 postoperative years), and those who had undergone thymectomy had consistently lower levels of new T cells and higher levels of pro-inflammatory molecules in the blood.

Scadden and his colleagues intend to investigate how different levels of thymus function in adults affect people's health.

“We can test the relative vigour of the thymus and define whether the level of thymus activity, rather than just whether it is present, is associated with better health,” he said.