Researchers at Mass General Brigham have uncovered evidence that the thymus, a small immune system organ long thought to lose its importance after childhood, may play a major role in adult health. Two new studies found that adults with healthier thymuses were more likely to live longer and less likely to develop serious diseases, as the research also suggests that thymic health may influence how well cancer patients respond to immunotherapy.

The findings were published in two papers in the same issue of Nature and challenge decades of assumptions about the thymus, and the results indicate that the organ remains important throughout adulthood and could eventually help guide disease prevention strategies and cancer treatment decisions.

Thymus: A Forgotten Immune System Component

“The thymus has been overlooked for decades and may be a missing piece in explaining why people age differently. Why cancer treatments fail in some patients,” said Hugo Aerts, PhD, corresponding author on the papers and director of the Artificial Intelligence in Medicine (AIM) Program at Mass General Brigham. “Our findings suggest thymic health deserves much more attention and may open new avenues for understanding how to protect the immune system as we age.”

Located in the chest, the thymus helps train T cells, a type of immune cell that helps defend the body against infections and disease.

Implications for Longevity and Cancer Treatment

The studies indicate that individuals with a healthier thymus have a significantly lower risk of heart disease, cancer, and mortality, and these findings could inform new strategies for disease prevention and treatment, particularly for cancer patients undergoing immunotherapy. Researchers are now exploring how to measure and improve thymic health as a potential intervention for aging and disease.

Broader Scientific Interest in Longevity

While the focus on the thymus is new, longevity research is also examining other organisms for clues. For example. Bowhead whales can live for more than 200 years, and scientists are investigating proteins in these whales that may contribute to their extended lifespan; such research could help extend human lifespan by uncovering mechanisms of cellular resilience and aging.

Researchers at Mass General Brigham used AI to analyze CT scans from tens of thousands of adults and found that people with healthier thymuses lived longer and had substantially lower risks of heart disease, cancer, and death. This marks a shift in how scientists understand the thymus—not as a dormant organ after childhood but as a critical player in adult health and disease resistance.