The Nobel Prize for 2025 in Physiology or Medicine goes to Mary E. Brunkow, Fred Ramsdell and Shimon Sakaguchi “for their discoveries concerning peripheral immune tolerance,” the Royal Swedish Academy of Sciences announced on Monday (October 6, 2025).

The laureates identified the immune system’s security guards, regulatory T cells, which prevent immune cells from attacking our own body.

Last year, the Medicine Nobel was jointly awarded to Victor Ambros and Gary Ruvkun for the discovery of microRNA and its role in post-transcriptional gene regulation.

The Prize for Physiology or Medicine kicks off a week of Nobel Prize announcements. The winners for Physics will be announced tomorrow (October 7), followed by Chemistry on October 8. The winners of the Literature, Peace and Economic Sciences Prize will be declared on October 9, October 10, and October 13 respectively.

The prizes carry a cash award of 10 million Swedish kronor (nearly $900,000) and will be awarded on December 10.

The Nobel Prize was created by Swedish inventor Alfred Nobel, who in his will dictated that his estate should be used to fund “prizes to those who, during the preceding year, have conferred the greatest benefit to humankind”.