The main function of the immune system is to protect its host against pathogenic bacteria, viruses and parasites. The immune cells and molecules participate also in tissue healing after injury, such as skin wounds. However, the immune system has also other important functions, not least in the brain. We investigate how the immune system, in particular its part called complement, affects brain development and function in health and in disease. We focus especially on the role of complement in the brain after stroke and birth asphyxia. Our aim is to find out how complement affects brain healing and functional recovery after injury by stimulating brain plasticity. Our main goal is to develop treatments to improve recovery of function after stroke and to minimize neurological impairments in children after birth asphyxia.