Researchers at the Walter and Eliza Hall Institute of Medical Research (WEHI) in Melbourne have discovered new cells that drive the aging process in the thymus that could unlock a way to restore function and prevent immunity from waning as we age. The thymus is the first organ in the body to shrink as people age. As this happens, the T-cell growth areas in the thymus are replaced with fatty tissue, diminishing T-cell production and contributing to a weakened immune system.