Buck Institute researchers discovered in an Alzheimer's disease mouse model that colonic immune cells, particularly CXCR4+ IgA-secreting B cells, migrate to the brain, potentially contributing to neuroinflammation. Elevated CXCL12 chemokine expression in brain glial cells appears to mediate this cellular trafficking. A high-fiber diet counteracted immune changes and mitigated Alzheimer’s pathology. These findings highlight the gut immune system's central role in neurodegenerative disease mechanisms and suggest dietary interventions as potential therapies.