Brain injuries lead to sustained neutrophil generation in the bone marrow and infiltration into the brain 3257

Abstract Description Neutrophils heavily infiltrate the brain following acute and chronic brain insults. Neutrophils infiltrating brain tumors display a prolonged lifespan compared to blood neutrophils. We investigated presence and potential function of neutrophils in the brain following infection with Theiler’s Murine Encephalomyelitis (TMEV) and kainic acid-induced seizures. Both total myeloid cells and neutrophils started infiltrating the brain as early as day 1, peaked at day 3, and remained elevated at least 7 days post-infection. Further characterization of the neutrophils revealed upregulation of MHC-II, indicating a potential role in antigen presentation. We detected similar accumulation of total myeloid cells and neutrophils in the brain of mice following seizures. MHC-II expression was upregulated on infiltrating neutrophils. Given the sustained and unusual accumulation of neutrophils in the brain past innate time points, we evaluated the bone marrow niche for evidence of myelopoiesis. Frequencies of Lin-Sca-1+c-Kit + (LSK) were significantly higher in all bone marrow compartments in mice infected intracranially with TMEV. This increase in LSK cells concurred with an increase in frequencies of total myeloid cells. These changes were not observed when mice were infected with TMEV systemically. Our data highlights dysregulation of bone marrow hematopoiesis and a potential novel role of neutrophils in response to neuroinflammation following intracranial pathologies. Topic Categories Neuroimmunology (NEUR)