x     The 2025 Nobel Prize in Medicine or Physiology was awarded to Mary E. Brunkow and Fred Ramsdell from the United States and Shimon Sakaguchi from Japan for their “discoveries concerning peripheral immune tolerance.” The winners identified the mechanisms, involving specific T cells (like the previously discovered CD25 cells), responsible for the self-regulation of the immune system. This mechanism, known as peripheral immune tolerance, prevents the immune system from attacking the body's