CD71 is a homodimer composed of two glycoproteins, with a molecular weight of 90-95kD, encoded by the gene on chromosome 3. CD71 is the transferrin receptor, primarily regulating iron intake in erythroid and proliferating cell populations. As a result, CD71 is expressed on a variety of cells, including nucleated red blood cells and their precursors, T and B cell precursors, centroblasts and centrocytes, activated T cells, activated NK cells, and follicular dendritic cells. Upon PHA stimulation, CD71 appears on the membrane of T cells after 24 hours, with about 88% of cells detectable for CD71 after 96 hours. CD71 can also be expressed on eosinophils, a small subset of neutrophils in patients treated with G-CSF, and eosinophils in allergic patients.
