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

可溶性转铁蛋白受体(STfR)的浓度被广泛认为是反映红细胞压积和细胞内铁水平的良好血清标志物。目前已有几种检测血清sTfR的试剂盒问世，但不同EIJSA试剂盒的sTfR测定值不同。这些差异主要是由sTfR的标准和所使用的mAbs引起的。因此，弄清血清中天然sTfR复合体的分子形式对于sTfR检测的标准化具有重要意义。我们用亲和层析法从人血清中分离纯化了sTfR复合体，并用抗TfR单抗进行了亲和层析。STfR复合体被认为是由两个sTfR和一个转铁蛋白(Tf)组成，复合体中sTfR和Tf的比例随血清铁浓度和Tf的铁饱和度而变化。然后，我们制备了三种针对TfR不同表位的单抗，并用这两套ELISA检测了来自血液病(缺铁性贫血：IDA)和非血液病(慢性肝炎：CH和类风湿关节炎：RA)的sTfR复合体的抗体反应性。慢性支气管炎和类风湿性关节炎患者sTfR的抗原性与IDA不同。由于CH和RA中sTfR的增加来源于非红系细胞，提示红系和非红系细胞的sTfR结构不同。这些结果表明，红系细胞来源的sTfR具有特殊的结构，建立针对该结构的sTfR检测体系将有助于评价红细胞的真实生成和红系状态。

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.