ISOLATION AND STRUCTURE ANALYSIS OF SOLUBLE TRANSFERIN RECEPTOR FOR INTERNATIONAL ASSAY SYSTEM

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The concentration of soluble transferrin receptors (sTfR) is widely recognized as a good serum marker reflecting the total erythropoirsis and intracellular iron levels of erythron. While, several ELISA kits to quantify serum sTfR have been developed, the values of scram sTfR are different among these EIJSA kite. These differences are mainly caused by the standard of sTfR and the mAbs to be used. Therefore, it is important to clarify the molecular form of native sTfR complex in serum for standardization of the sTfR assay. We elucidated the structure of purified sTfR complex obtained from human serum without a detergent and dissociation procedure by means of affinity chromolography using monoclonal anti-TfR antibody. The sTfR complex was considered to be composed of two sTfR and one transferrin (Tf) and the ratio of sTfR and Tf in the complex would change depend on the serum iron concentration and iron saturation of Tf. We then developed three monoclonal antibodies against different epitopes of TfR and investigated the antibody-reactivity against sTfR complex derived from hematopoietic disease (iron deficiency anemia: IDA) and non-hematopoielic disease (chronic hepatitis: CH and rheumatoid arthritis: RA) using the two sets of ELISA. The antigenesity of sTfR in CH and RA was different from that in IDA. Because the sTfR increased in CH and RA was derived from non-erythroid cell, sTfR structure was suggested to be different between erythroid and non-erythroid cells. These results suggest thatthe sTfR derived from erythroid cell has a specific structure and the establishment of sTfR assay system against this structure will be useful to evaluate the true erythropoiesis and iro status of erythron.