Figure 1. Identification of epiplexus cells as immune cells. (A) Scheme of the experimental approach. (B) CPs are located in all four brain ventricles. (C) An acutely isolated and intact CP from the lateral ventricle. Scale bar is approximately 1 mm. (D) A living epiplexus cell resting on the choroidal epithelium, visualized with transmitted light (left) or by labeling with Alexa Fluor 488 isolectin B4 conjugate from Griffonia simplicifolia (center); EC – epiplexus cell, EP – choroidal epithelium, BV – blood vessel, LV – lumen of the lateral ventricle. Scale bar is 20 μm. (E) Immunofluorescent staining for immune cell markers, Iba1 and IB4 in the CP. Note the significant co-localization (yellow cells in the merge image). Scale bar is 20 μm.