One main reason your immune system fails with age appears to be that chronic infections by the likes of cytomegalovirus (CMV) cause too many of your immune cells to be - uselessly - specialized. As noted in the New Scientist, researchers are looking into a possible way of clearing these infections from the body: they "studied an acute and chronic meningitis infection in mice, called lymphocytic choriomeningitis virus (LCMV). They discovered that mice with chronic infections had high levels of the inflammatory-damping chemical interleukin-10 (IL-10). When they gave mice with chronic LCMV a drug that blocks the inflammatory-calming action of IL-10, the inflammatory immune response was re-activated. Within a week the mice were healthier. In two weeks, they had cleared the virus completely." Now if this could be turned against CMV early in life, the immune system would look a lot better later on - but a method of cleaning out the uselessly specialized cells would be needed to help those suffering now.