Nature Communications, Published online: 24 August 2026; doi:10.1038/s41467-026-76817-5 The role of B cells in vascular cognitive impairment is unclear. Here, the authors show a crosstalk between CNS border-associated B cells and parenchymal microglia, through MIFCD74/CXCR4 and IgG signaling, exacerbating white matter injury.