The antiaging power of blood might not be just the stuff of vampire stories. According to new research from Harvard University, an unspecified factor in the blood of young mice can reverse signs of aging in the circulatory system of older ones. It’s not yet clear how these changes affect the animals’ overall health or longevity. But the research provides hope that some aspects of aging, such as the age-related decline in the ability to fight infection, might be avoidable.

“At least some age-related defects are reversible, and the factors to reverse them are carried in blood,” said Amy Wagers, a researcher at the Harvard Stem Cell Institute and Joslin Diabetes Center, in Boston, at a press conference on Tuesday. Identifying those factors could lead to new strategies to boost resistance to infection, and perhaps a decrease in some cancers, she said.

In the experiment, Wagers and team surgically connected the circulatory systems of two mice, allowing older animals to be exposed to blood–and all the molecules and cells it carries– from young animals. They found that the procedure made the blood-forming stem cells in older animals act young again; the overall number of these cells decreased, and the cells generated different varieties of blood cells in more appropriate ratios. “In aged animals, many of the changes we see normally that are associated with age were reversed,” said Wagers.

via Technology Review: Young Blood Reverses Signs of Aging in Old Mice.