FatLittleMonkey writes "A new study on mice suggests damage caused by diseases like Multiple sclerosis, as well as natural aging, can be reversed by an infusion of stem cell rich blood from younger mice. Multiple sclerosis is a chronic inflammatory disease that erodes the fatty myelin sheaths around the axons of the brain and spinal cord, and can result in serious disability. Similar effects occur naturally with aging. From New Scientist: 'White blood cells called macrophages from the young mice gathered at the sites of myelin damage. Macrophages engulf and destroy pathogens and debris, including destroyed myelin. "We know this debris inhibits regeneration, so clearing it up is important," says team member Amy Wagers of Harvard University.' Here's the academic paper's abstract."