In a groundbreaking revelation, the thymus gland, often dismissed as insignificant in adulthood, has been shown to hold a critical role in human health, according to a recent retrospective study conducted by US researchers. The study uncovers surprising links between thymus removal and increased mortality risk as well as cancer development, prompting experts to rethink the importance of this seemingly 'useless' gland.
"The magnitude of risk was something we would have never expected. 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," 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.
Researchers discovered that individuals who underwent thymus removal faced a significantly elevated risk of death from any cause later in life. Moreover, these individuals were found to be more susceptible to developing cancer.
The thymus gland, responsible for fostering the development of the immune system during childhood, has shown to result in long-term reductions in T-cells—white blood cells vital for combating illnesses—when removed at a young age.`
Additionally, individuals without a thymus tend to exhibit weakened immune responses to vaccines.
"The magnitude of death and cancer in patients who had undergone thymectomy was the biggest surprise for me. The more we dug, the more we found: The results suggested to us that the lack of a thymus appears to perturb basic aspects of immune function," said first author Kameron Kooshesh, now an internal medicine resident at MGH.
Contrary to the belief that the thymus diminishes in importance after puberty, this study challenges that notion. Patients who had undergone thymus removal were almost twice as likely to die within five years compared to those who retained their thymus. This heightened risk persisted even after accounting for factors such as sex, age, race, cancer of the thymus, myasthenia gravis, or postoperative infections.
The findings also highlighted a two-fold increase in cancer development within five years post-surgery for thymus removal. Furthermore, this cancer displayed greater aggression and recurrence rates, setting it apart from cancers in the control group.
While the exact mechanisms behind these associations remain unclear, researchers speculate that the absence of the thymus might disrupt the healthy functioning of the adult immune system. Notably, patients who underwent thymectomy exhibited fewer diverse T-cell receptors in their bloodwork, which could potentially contribute to the emergence of cancer or autoimmune diseases following surgery.
The findings of the study were published in The New England Journal of Medicine.