A tissue protein, also found in blood serum, which has a specific recognition-affinity for the iron-transporting protein, transferrin. It increases in concentration in conditions of chronic iron deficiency, and is therefore used as an iron status indicator. Unlike most other iron status indices, it is not confounded by the presence of an acute phase reaction (q.v.)
The receptor molecule (located on the surface of cells throughout the body) that is responsible for binding to transferrin molecules, then bringing those iron-rich transferrin molecules into the cell where the iron is released to be used by the cell.