Intestinal challenges shape the polarisation of protective dural memory CD4 T cells

The meninges house several innate and adaptive immune cell populations^1–3. These predominantly localise within the dura mater and include gut-derived IgA-secreting plasma cells⁴. Whether T cell adaptive memory in the dura is similarly linked to the gut is currently unknown. Here we show that dural CD4 T cell polarisation to a T helper (Th) 1, Th2 and Th17 state is determined by the nature of the immunological challenge encountered in the gastrointestinal tract. We find that intestinally polarised CD4 T cells seed to the dura in a CXCR6-CXCL16-dependent manner, express tissue-residency markers and are long-lived. Functionally, these orally-primed dural CD4 T are capable of a rapid antigen-specific recall response that limits pathogen spread into the brain following intravenous re-challenge. Our work reveals how linked intestinal and dural immunity enables the central nervous system to accrue immunological memory of gut microbes, the most likely source of life-threatening bloodborne pathogens.