Americans Mary E. Brunkow and Fred Ramsdell win the Nobel Prize in Medicine

U.S. scientists Mary E. Brunkow and Fred Ramsdell, along with Japan's Shimon Sakaguchi, won the Nobel Prize in Medicine for their research on how the body controls the immune system.

The three were honored for their "discoveries on peripheral immune tolerance," the Nobel committee announced in a statement.

"The body’s powerful immune system must be regulated, or it may attack our own organs," the Nobel committee stressed.

The laureates, Mary E. Brunkow, 64, Fred Ramsdell, 64, and Shimon Sakaguchi, 74, "identified the immune system’s security guards, regulatory T cells, which prevent immune cells from attacking our own body," it added.

"Their discoveries have been decisive for our understanding of how the immune system functions and why we do not all develop serious autoimmune diseases," the jury explained.