Immune System's Secret Security Guards Nab Nobel Prize for Autoimmune Breakthrough

Three scientists have been awarded the Nobel Prize in Physiology or Medicine for 2025 for their groundbreaking discoveries about the immune system. Shimon Sakaguchi from Japan, along with Mary Brunkow and Fred Ramsdell from the United States, were recognized for their work explaining how the immune system can fight off dangerous infections without attacking the body's own cells. Their research led to the discovery of regulatory T-cells, which act like security guards, making sure the immune system does not harm healthy tissues.

The immune system is made up of white blood cells that search for and destroy harmful invaders like viruses and bacteria. These cells use special sensors called receptors, which are created in many different combinations. This allows the immune system to recognize and fight a wide variety of infections. However, because the process is random, some white blood cells can end up attacking the body's own tissues. Scientists already knew that some of these harmful cells are destroyed in the thymus, an organ where white blood cells mature.

The Nobel Prize was awarded for the discovery of regulatory T-cells, which travel throughout the body and stop other immune cells from attacking healthy tissues. When this system fails, people can develop autoimmune diseases such as type-1 diabetes, multiple sclerosis, and rheumatoid arthritis. The scientists' work has helped create new treatments for these diseases and for cancer. In cancer, regulatory T-cells can prevent the immune system from attacking tumors, so researchers are working on ways to reduce their numbers. For autoimmune diseases, doctors are trying to increase the number of regulatory T-cells to stop the body from attacking itself. This research could also help prevent organ rejection in transplant patients.

Professor Sakaguchi showed that mice without a thymus developed autoimmune diseases, but injecting them with immune cells from other mice could prevent these diseases. Mary Brunkow and Fred Ramsdell discovered a gene that is important for regulatory T-cells to work properly. Their discoveries have opened up a new field of research and have had a big impact on human health. Professor Annette Dolphin said their work is a great example of how basic science can lead to important medical advances.