ROCHESTER, Minn. -- The immune system is meant to protect the body from infection and disease. But with age, it can become less capable of doing so. However, Mayo Clinic researchers have found that some older people maintain "immune youth" -- a new term for a young immune system in someone older than 60.

"We are studying why some individuals have a 'fountain of youth' in their immune systems. We want to learn from them," said Dr. Cornelia Weyand, a Mayo Clinic rheumatologist and clinician-scientist. She is a lead author on a perspective paper published in Nature Aging.

Weyand's research team discovered this cellular fountain of youth in more than 100 older patients who came to Mayo Clinic to receive treatment for an autoimmune disease that affects the arteries, including the aorta, called giant cell arteritis. Weyand and colleagues found in the diseased tissue of these patients specialized immune cells, called stem-like T cells. These behave like young stem cells that usually regenerate and aid healing and growth; but in this case, they were spreading the disease. This team of researchers also discovered autoimmune stem cells in humans previously.

"We observed that these patients have very young immune systems despite being in their 60s and 70s. But the price they pay for that is autoimmunity," she said.