Traumatic brain injuries (TBIs) can cause lasting damage, but stopping the rampant brain inflammation they cause is difficult. A team at the Wyss, @SEAS and @MGH led by Samir Mitragotri has made a new treatment using macrophages — immune cells that migrate to the brain. By attaching microparticle ‘backpacks’ that kept the macrophages in a healing state, they reduced the size of brain lesions by 56% in pigs with a mock TBI.