Weakened immunity is a serious issue for older people, as immune systems become less effective as we age, putting us at-risk for serious infections that can compromise health and quality of life. Until now, ageing in immune cells was thought to be largely determined by the length of telomeres, endcaps on DNA, that shorten each time a white blood cell multiplies until, when they get too short, the cell gets permanently deactivated. Arne N. Akbar, from University College London (United Kingdom), and colleagues analyzed white blood cells closely, finding that some were inactive and yet had long telomeres. The researchers posited that there must be another mechanism in the immune system causing cells to become deactivated that was independent of telomere length. When the researchers blocked this newly identified pathway in the lab, they found that the white blood cells appeared to be reactivated. Observing that [immune system cells] demonstrate a “telomere-independent senescence that are regulated by active cell signaling pathways that are reversible,” the researchers are next exploring whether white blood cells can be reactivated in older people, opening  up the exciting possibility of giving older people's immune systems a temporary boost to help them fight off infections.