Fig. 4

Migration of CD56^bright and CD56^dim NK cells across the blood–brain barrier. The blood–brain barrier (BBB) is formed by the closely connected brain endothelial cells that line the vessels, their basement membrane, pericytes and the astrocytic end-feet or glia limitans [89]. While the exact molecular interactions that allow NK cell migration across the BBB are currently unknown, a small proportion of NK cells can cross this barrier under unstimulated conditions, with CD56^bright NK cells migrating towards the brain in higher numbers that CD56^dim NK cells [61]