As we age, our immune systems age too. They can start sending off false alarms and attacking the body's healthy cells, while becoming less responsive to actual threats. Ann Griffith, PhD, is an assistant professor in the Department of Microbiology, Immunology, and Molecular Genetics in the Joe R. and Teresa Lozano Long School of Medicine at UT Health San Antonio, and she studies what that means for human health.
“We're interested in the ways that our immune system changes with age,” Griffith said. “Part of that is becoming less responsive to infections and vaccines and also becoming over-responsive to ourselves.”
We’ve seen how that can play out during the COVID pandemic. The immune systems of older adults didn’t fight off the novel virus as well as those of younger people. They also didn’t respond as well to vaccines, leaving this already vulnerable population without complete protection. Additionally, over-responsiveness to healthy cells can lead to autoimmunity, which can cause damaging chronic inflammation.
Griffith runs UT Health San Antonio’s Griffith Lab, where they’re studying the thymus. The thymus is an organ in the immune system that atrophies with age. Over the years, researchers have found ways to restore a youthful plumpness to an aging thymus but have not figured out a way to improve its function for very long. Griffith suspected it might all come down to T cells.
“T cells are important for fighting infections that happen in our own cells, or when our own cells are transformed, as tumors begin to develop. Older folks have fewer T cells, and they have a more narrow T cell repertoire,” Griffith explained.
T cells learn how to fight invaders in the thymus. Griffith wondered if a protein called fibroblast growth factor 21 — FGF21— might be a kind of fountain of youth for the thymus, restoring its function as a T cell training center, increasing the number and variety of battle-ready T cells. She studied aging mice with higher levels of FGF21 with a couple of questions in mind.
“Do they respond better to viral infections, and do we improve their autoimmunity along with improving the response to infection? We saw that, in fact, they did,” Griffith concluded.
That’s in mice, though. What might a youthful thymus mean for human immunity? More study is ahead, Griffith said, but she thinks FGF21 could be used to boost thymus function before a person receives a vaccine, which might improve its effectiveness. FGF21 might also help restore the T cell population when it has been diminished by treatments like chemotherapy or bone marrow transplantation.
Science & Medicine is a collaboration between TPR and The University of Texas Health Science Center at San Antonio, about how scientific discovery in San Antonio advances the way medicine is practiced everywhere.
