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总红细胞生成和胞内铁水平的良好血清标志物。虽然目前已有多种ELISA试剂盒用于检测血清sTfR，但各EIJSA风筝的血清sTfR测定值存在差异。这些差异主要是由sTfR的标准和所用的mAb引起的。因此，澄清血清中天然sTfR复合物的分子形式对于sTfR测定的标准化是重要的。我们阐明了纯化的sTfR复合物的结构，从人血清中获得无洗涤剂和解离程序通过亲和色谱法使用单克隆抗TfR抗体。sTfR复合物由两个sTfR和一个转铁蛋白（Tf）组成，复合物中sTfR和Tf的比例随血清铁浓度和Tf的铁饱和度而变化。然后，我们开发了三种针对不同表位的TfR的单克隆抗体，并使用两组ELISA研究了对来自造血系统疾病（缺铁性贫血：IDA）和非造血系统疾病（慢性肝炎：CH和类风湿性关节炎：RA）的sTfR复合物的抗体反应性。sTfR在CH和RA中的抗原性与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sTfR结构不同。这些结果表明，红系细胞来源的sTfR具有特异性结构，建立针对该结构的sTfR检测体系将有助于评价红系细胞的真实红细胞生成和红细胞功能状态。

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.