Relationship between soluble transferrin receptors in serum and membrane-bound transferrin receptors.

The expression of transferrin receptors on the cell membrane of erythroblasts was analysed with flow cytometry in patients with different forms of anaemia. At the same time the concentration of soluble transferrin receptors (sTfRs) was analysed in serum. It was shown that only in iron deficiency a high concentration of sTfRs in serum could be explained with an increased expression of transferrin receptors on the erythroblastic membrane. In anaemia of chronic disease and myelodysplasia a discrepancy between a low expression on the cell membrane and normal or elevated serum values was seen. From this study we conclude that the concentration of sTfRs in serum does not only depend on the expression of transferrin receptors on the erythroblasts but also on the erythroid activity.