Microglia Get a Little Help from "Th"-eir Friends.

The presence of CD4+ T cells in the healthy brain parenchyma remains controversial due to the barrier function of the glia limitans. Pasciuto, Burton, Roca et al. in Cell describe the dynamic recruitment of CD4+ T cells within the brain parenchyma, their unexpected contribution to microglial maturation, and, ultimately, their influence on behavior.