The brain is the most complicated structure that we know about. It houses billions of nerve cells (neurones) and millions of kilometres of connections which allow us to move, breath, think and remember. Even a small injury to part of the brain can be devastating, and brain diseases pose the greatest burden on society, affecting an increasing number of people and their families. Nancy Rothwell’s research group has been trying to find out what causes damage or death of brain cells in diseases such as stroke, brain injury and Alzheimer disease. They have discovered that a protein called interleukin-1 (IL-1) is an important “killer molecule” which is switched on after insults to the brain. A naturally occurring blocker of IL-1, called IL-1ra, reduces experimental damage to the brain and Nancy’s team has just completed the first clinical trial of IL-1ra in stroke patients.