Microglial cells become activated rapidly after brain injuries and produce chemokines that attract macrophages, which are generally viewed as contributing to secondary and tertiary brain injury.39,40 In our previous study, we found that there was a progressive accumulation of reactive microglia/macrophages in LIF-haplodeficient mice after mTBI.9 By contrast, we show here that IN-LIF reduces microglia hypertrophy and that the microglia are less activated as assessed by decreased expression of the lysosomal protein, CD68. Here, LIF is linked to concussion.