A tiny organ in our chest cavity could be the key to regulating inflammation as we age, according to new research in mice.
The thymus is nestled between our lungs and is roughly the size of a dried apricot. It helps our bodies produce pathogen-fighting immune cells called T cells, particularly in childhood. After puberty, it shrinks—and scientists long thought its role in our immune system likely shrank, too.
But its job may not end there at all: a hormone secreted by the thymus called thymulin appears to clamp down on age-related inflammation in older mice.
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If the results are confirmed in humans, researchers say, they could help scientists develop new cancer therapies and treatments for other diseases associated with “inflammaging”—inflammation that develops with age. The findings were published on Tuesday in the journal Nature Communications.
The hormone thymulin was discovered some 50 years ago, but its role in aging has been “somewhat overlooked,” says Fumito Ito, the study’s senior author and an immunologist at the Keck School of Medicine of the University of Southern California.
Previous research has linked thymus health to immune function and longevity. In March, as Scientific American reported, an analysis of around 27,000 patient records found that thymus function correlated with longer lifespans, as well as lower rates of lung cancer or cardiovascular disease. Thymus health also tracked with inflammation—but it was unclear why.
The new findings may provide a “causal link” between the thymus and longevity, Ito says. In mice with higher levels of thymulin, a group of their immune cells called myeloid cells tended to produce lower levels of cytokines, a kind of protein that our bodies make to fight off infections but that can also lead to inflammation. Even more compelling, when the researchers gave thymulin to older mice with cancer, the animals responded better to treatment and had slower rates of tumor growth.
The results could one day improve cancer therapies for humans, Ito says. “Our study shows that this hormone can slow down tumor growth, improve survival and also enhance the treatment efficacy of cancer immunotherapy,” he says.
“Given the fact that this is naturally occurring hormone,” Ito adds, “I expect that the use of this hormone would cause minimal side effects, while it can potentially improve the treatment efficacy of immunotherapy.”
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