Yamamura Y, Kotani M, Tsudo M, Karasuyama H, Seto A, Miyasaka M
Department of Immunology, Tokyo Metropolitan Institute of Medical Science, Japan.
Immunology. 1990 Dec;71(4):502-7.
Low-affinity (dissociation constant: Kd = 7 nM) and high-affinity (Kd = 27 pM) interleukin-2 receptors (IL-2R) were detected on rabbit T-cell lines by IL-2 binding studies. Chemical cross-linking studies using 125I-labelled IL-2 showed that rabbit low-affinity IL-2R was singly expressed alpha-chain (MW 55,000) and that high-affinity IL-2R was composed of at least alpha- and beta- (MW 75,000) chains, similar to the human and murine counterparts. The existence of an additional chain (MW 25,000) was suggested in the rabbit IL-2R. Rabbit T-cell transfectant lines were established by human IL-2R alpha-chain (IL-2R alpha) cDNA transfection. These transfectant lines possessed not only extremely large numbers of human IL-2R alpha (over 10 times more than endogenous rabbit alpha-chain) but also twice as many high-affinity sites as their parental lines. The number of high-affinity sites on the transfectants significantly decreased when human alpha-chains were blocked, indicating that these transfectants expressed high-affinity receptor consisting of the exogenous human alpha-chain and rabbit beta-chain. This was confirmed by cross-linking experiments. The observation that expression of extremely large numbers of exogenous alpha-chains lead to an increase of the total number of high-affinity sites in the apparent absence of an increase of beta-chain expression raises the possibility that not only the beta-chain but also the alpha-chain may play an important role in regulating the number of high-affinity receptors.
通过白细胞介素-2（IL-2）结合研究在兔T细胞系上检测到低亲和力（解离常数：Kd = 7 nM）和高亲和力（Kd = 27 pM）的IL-2受体（IL-2R）。使用125I标记的IL-2进行的化学交联研究表明，兔低亲和力IL-2R单独表达α链（分子量55,000），高亲和力IL-2R至少由α链和β链（分子量75,000）组成，类似于人类和小鼠的对应物。在兔IL-2R中提示存在另一条链（分子量25,000）。通过人IL-2Rα链（IL-2Rα）cDNA转染建立兔T细胞转染系。这些转染系不仅拥有极大量的人IL-2Rα（比内源性兔α链多10倍以上），而且其高亲和力位点数量是亲代系的两倍。当人α链被阻断时，转染体上的高亲和力位点数量显著减少，表明这些转染体表达由外源性人α链和兔β链组成的高亲和力受体。交联实验证实了这一点。在明显没有β链表达增加的情况下，极大量外源性α链的表达导致高亲和力位点总数增加，这一观察结果提示不仅β链而且α链可能在调节高亲和力受体数量方面发挥重要作用。
