Researchers have found that immune cells called microglia which play an important role in reorganising the connections between nerve cells fighting infections and repairing damage are also primarily active while we sleep. Microglia serve as the brain's first responders patrolling the brain and spinal cord and springing into action to stamp out infections or gobble up debris from dead cell tissue. This research shows that the signals in our brain that modulate the sleep and awake state also act as a switch that turns the immune system off and on said study lead author Ania Majewska Professor at University of