Stromal Cell Niches in the Inflamed Central Nervous System.

Inflammation in the CNS must be tightly regulated to respond efficiently to infection with neurotropic pathogens. Access of immune cells to the CNS and their positioning within the tissue are controlled by stromal cells that construct the barriers of the CNS. Although the role of the endothelium in regulating the passage of leukocytes and small molecules into the CNS has been studied extensively, the contribution of fibroblastic stromal cells as portals of entry into the CNS was only recently uncovered. We review the critical immune-stimulating role of meningeal fibroblasts in promoting recruitment and retention of lymphocytes during CNS inflammation. Activated meningeal fibroblastic stromal cells have the capacity to rapidly elaborate an immune-competent niche that sustains protective immune cells entering the CNS from the draining cervical lymph node. Such stromal cell niches can ultimately foster the establishment of tertiary lymphoid tissues during chronic neuroinflammatory conditions.