Figure 3.

Tf crosses the BBB through transcytosis, a form of endocytosis. Fe+2 (free iron) is exported from the macrophage through ferroportin (FPN) and binds to Tf, which then binds to the TfR on the BBB. The TfR receptor then delivers iron to the brain, and the amount of iron in the brain increases.¹³ Reprinted with permission from ref (13). Copyright 2018 Chiou et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.