By generating a compartment-specific transcriptional map of meningeal versus parenchymal leukocytes in experimental neuroinflammation, we found a follicular phenotype of meningeal B cells and a corresponding follicular helper-like phenotype in meningeal Th17 cells. The meninges thus instructed a site-specific local phenotype to proinflammatory autoreactive T cells. We identified the transcription factor Bcl6 in Th17 cells to promote interactions with meningeal B cells, isotype-switching, and B cell-supporting chemokines. This may describe a mechanism controlling meningeal autoimmunity and helps understanding how the meninges, as a recently recognized immunologically active site, contribute to autoimmune tissue damage in multiple sclerosis.
