Fig. 1.

A schematic of the choroid plexus illustrates that the choroidal capillaries are separated from the CSF by a layer of choroidal epithelial cells. If the choroid plexus acted as a site of brain iron uptake, Tf released by the blood would bind to TfR on the membrane nearest to the capillary, and iron would cross to the membrane that faces the CSF, and be exported by FPN, aided by a ferroxidase such as ceruloplasmin or hephaestin. In this potential scheme, DMT1 would be needed to release iron from endosomes after internalization of the Tf-TfR complex, and an endosomal reductase would also be needed. This figure was reproduced from http://www.daviddarling.info/encyclopedia/copyright.html with permission from David Darling