PD-1 in hippocampal neurons regulates excitability, synaptic plasticity, and cognition

Immunotherapy using monoclonal antibodies against programmed cell death protein 1 (PD-1) demonstrated improved survival in cancer patients through immune activation. Here we show that functional PD-1 is expressed in mouse and primate hippocampal neurons and PD-1 inhibition improves cognition in physiological and pathological conditions. Mice lacking the Pdcd1 gene encoding PD-1 exhibit enhanced long-term potentiation (LTP) and learning and memory. These behavioral and cellular changes can be recapitulated by selective deletion of Pdcd1 in hippocampal excitatory neurons but not in microglia. Perfusion of mouse or nonhuman primate brain slices with anti-PD-1 antibody is sufficient to increase excitability in CA1 hippocampal neurons. Conversely, re-expression of Pdcd1 in PD-1 deficient hippocampal neurons suppresses memory and LTP. Traumatic brain injury impairs learning and memory, which is improved by intraventricular administration of anti-PD-1. These findings suggest that anti-PD-1 treatment has therapeutic potential to counteract cognitive decline. HighlightsO_LIAdult mice lacking Pdcd1 in hippocampal neurons exhibit enhanced memory and LTP C_LIO_LIAnti-PD-1 antibody treatment increases CA1 neuron excitability in brain slices of mice and primates C_LIO_LIRe-expression of Pdcd1 in PD-1 deficient hippocampal neurons impairs memory and LTP C_LIO_LICognitive deficits after traumatic brain injury are improved by anti-PD-1 treatment C_LI