Chronic social defeat stress induces meningeal neutrophilia via type I interferon signaling in male mice.

Inflammation is increasingly recognized as a risk factor for psychiatric disorders. Animal models of stress and stress-related disorders are associated with blood neutrophilia. The mechanistic relevance of this to symptoms or behavior is unclear. We characterized the immune response to chronic social defeat (CSD) stress at brain border regions in male mice. Here we show that chronic, but not acute, stress causes neutrophil accumulation in the meninges-i.e., "meningeal neutrophilia"- but not the brain. CSD promotes neutrophil trafficking to meninges via vascular channels originating from skull bone marrow (BM). Transcriptional analysis suggests CSD increases type I interferon (IFN-I) signaling in meningeal neutrophils. Blocking this pathway via the IFN-I receptor (IFNAR) protects against the negative behavioral effects of CSD stress. Our identification of IFN-I signaling as a putative mediator of meningeal neutrophil recruitment may facilitlate development of new therapies for stress-related disorders.