ABSTRACT
Interleukin (IL)-17a has been highly conserved during evolution of the vertebrate immune system and widely studied in contexts of infection and autoimmunity. Studies suggest that IL-17a promotes behavioral changes in experimental models of autism and aggregation behavior in worms. Here, through a cellular and molecular characterization of meningeal γδ17 T cells, we defined the nearest central nervous system-associated source of IL-17a under homeostasis. Meningeal γδ T cells express high levels of the chemokine receptor CXCR6 and seed meninges shortly after birth. Physiological release of IL-17a by these cells was correlated with anxiety-like behavior in mice and was partially dependent on T cell receptor engagement and commensal-derived signals. IL-17a receptor was expressed in cortical glutamatergic neurons under steady state and its genetic deletion decreased anxiety-like behavior in mice. Our findings suggest that IL-17a production by meningeal γδ17 T cells represents an evolutionary bridge between this conserved anti-pathogen molecule and survival behavioral traits in vertebrates.
Subject(s)
Anxiety/etiology , Anxiety/metabolism , Interleukin-17/metabolism , Neurons/immunology , Neurons/metabolism , Receptors, Antigen, T-Cell, gamma-delta/metabolism , T-Lymphocyte Subsets/immunology , T-Lymphocyte Subsets/metabolism , Animals , Anxiety/psychology , Behavior, Animal , Cell Proliferation , Cerebral Cortex/metabolism , Cerebral Cortex/physiopathology , Disease Models, Animal , Dura Mater , Gene Expression Profiling , Gene Expression Regulation , Interleukin-17/genetics , Meninges/immunology , Meninges/metabolism , Mice , Mice, Knockout , Receptors, Antigen, T-Cell, gamma-delta/genetics , Signal Transduction , TranscriptomeABSTRACT
The meninges are a membranous structure enveloping the central nervous system (CNS) that host a rich repertoire of immune cells mediating CNS immune surveillance. Here, we report that the mouse meninges contain a pool of monocytes and neutrophils supplied not from the blood but by adjacent skull and vertebral bone marrow. Under pathological conditions, including spinal cord injury and neuroinflammation, CNS-infiltrating myeloid cells can originate from brain borders and display transcriptional signatures distinct from their blood-derived counterparts. Thus, CNS borders are populated by myeloid cells from adjacent bone marrow niches, strategically placed to supply innate immune cells under homeostatic and pathological conditions. These findings call for a reinterpretation of immune-cell infiltration into the CNS during injury and autoimmunity and may inform future therapeutic approaches that harness meningeal immune cells.