Figure 2: Transmigration of immune cells across the choroid plexus into the CSF. Under the influence of chemokines immune cells in the small choroidal capillaries undergo adhesion, rolling and finally diapedesis into the stroma. There, the cells might be attracted by additional chemokines, produced by the CSF-secreting epithelial cells of the choroid plexus (Kolmer cells), thus resulting in migration through the epithelial cell layer into the ventricle. Abbreviation: CSF: Cerebro Spinal Fluid. Illustration modified from Wilson et al. [17] and Ransohoff et al. [16].