In mice, intestinal infections reshaped dural CD4+ T-cell populations and seeded the brain’s outer meningeal border with antigen-specific memory cells that persisted for months and mounted rapid recall responses to bloodborne antigens. Oral priming was associated with reduced Salmonella spread to the brain and modest cross-protection in an engineered shared-antigen Candida model, although the researchers could not definitively prove that dural CD4+ T cells alone caused the protection.