The role of immune responses in the cognitive impairments associated with tauopathy is unclear. Laurent et al. identify a CD8+ T-cell infiltration in the hippocampus of THY-Tau22 transgenic mice. T-cell depletion reverses spatial memory deficits in these animals, supporting a role for hippocampal T-cell infiltration in tau-driven cognitive impairments.

Physiological functions of tau remain ill defined. In the present study, Marciniak et al. uncover a novel function of tau in its ability to regulate brain insulin signaling and discuss the pathophysiological implications of these findings for Alzheimer’s disease and tauopathies.