The inflammatory mediator interleukin-1 (IL-1), which is known to be a driver of chronic diseases such as diabetes and hypertension, has recently been identified as a major contributor to ischaemic brain injury. IL-1 is made by the haematopoietic (blood) system and also by cells in the brain. The relative contributions of central versus peripheral sources of IL-1 to brain injury have not been previously investigated. Here, Stuart Allan and colleagues selectively eliminated haematopoietic-derived IL-1 in a chimeric mouse model of ischaemic brain injury. They demonstrate that both sources of IL-1 are important for disease development, but removal of the peripheral source alone is sufficient to improve neurological outcome in the mice. This suggests that therapies that target peripheral IL-1 could be beneficial in brain injury, potentially overriding the need to deliver drugs across the blood-brain barrier. Page 1043

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.