The 2025 Nobel prize in physiology or medicine celebrates a discovery that answers one of medicine’s most profound questions: how does the immune system know when to attack, and when to stand down?
Most of the time, our defences target dangerous infections and even cancers while leaving the body’s own tissues unharmed. But when that balance fails, the consequences can be devastating – from autoimmune diseases, where the immune system turns on healthy organs, to cancers, where it becomes too restrained to recognise and destroy tumour cells.
