Nakarai T, Robertson M J, Streuli M, Wu Z, Ciardelli T L, Smith K A, Ritz J
Division of Hematologic Malignancies, Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
J Exp Med. 1994 Jul 1;180(1):241-51. doi: 10.1084/jem.180.1.241.
The interleukin 2 receptor (IL-2R) is known to be comprised of at least three genetically distinct subunits termed alpha, beta, and gamma. These chains can be expressed individually or in various combinations resulting in distinct receptors with different affinities for IL-2. In contrast to alpha and beta, the cell surface expression of the gamma chain protein previously has not been well-characterized. To examine cell surface expression of IL-2R gamma on hematopoietic cells, we developed two new monoclonal antibodies (mAbs) specific for this protein. Both 1A11 (immunoglobulin [IgG1]) and 3G11 (IgM) specifically reacted with murine cells transfected with IL-2R gamma cDNA, and immunoprecipitation studies indicated that both antibodies precipitated a protein of approximately 62-65 kD. Scatchard analysis of IL-2 binding to murine cells transfected with cDNA-encoding combinations of IL-2R components demonstrated that neither beta nor gamma chain bind IL-2 with measurable affinity, but coexpression of both beta and gamma is sufficient to form an intermediate affinity receptor. In the absence of gamma chain, beta chain interacts with alpha chain to form a "pseudo-high" affinity receptor. In contrast, gamma chain does not appear capable of interacting with alpha in the absence of beta chain. Thus, gamma chain appears to interact only with beta, but beta chain is capable of interacting with both alpha and gamma. Using the newly developed mAbs to examine cell surface expression by immunofluorescence, resting T cells were found to express low levels of gamma chain without detectable alpha or beta. Early after mitogen stimulation, T cells expressed higher levels of alpha, beta, and gamma. However, at later time points, T cells expressed alpha and gamma in marked excess over beta. Thus, formation of high affinity IL-2R on activated T cells was primarily limited by beta chain expression. In contrast, resting natural killer (NK) cells constitutively expressed IL-2R beta without detectable alpha or gamma. After activation with either IL-2 or IL-12, expression of both alpha and gamma transiently increased and then returned to very low levels. Expression of functional IL-2R on resting and activated NK cells, therefore, appeared to be primarily limited by the expression of gamma chain. IL-2 binding studies with resting NK cells confirmed the results of immunofluorescence studies indicating the presence of very low numbers of intermediate affinity (beta gamma) receptors for IL-2 on these cells.(ABSTRACT TRUNCATED AT 400 WORDS)
白细胞介素2受体（IL-2R）已知至少由三个基因不同的亚基组成，分别称为α、β和γ。这些链可以单独表达或以各种组合表达，从而产生对IL-2具有不同亲和力的不同受体。与α和β不同，γ链蛋白在细胞表面的表达此前尚未得到很好的表征。为了研究IL-2Rγ在造血细胞上的细胞表面表达，我们开发了两种针对该蛋白的新型单克隆抗体（mAb）。1A11（免疫球蛋白[IgG1]）和3G11（IgM）都能与转染了IL-2Rγ cDNA的鼠细胞特异性反应，免疫沉淀研究表明这两种抗体都沉淀出一种约62 - 65 kD的蛋白质。对IL-2与转染了编码IL-2R成分组合的cDNA的鼠细胞结合的Scatchard分析表明，β链和γ链都不能以可测量的亲和力结合IL-2，但β链和γ链的共表达足以形成中等亲和力的受体。在没有γ链的情况下，β链与α链相互作用形成“假高”亲和力受体。相反，在没有β链的情况下，γ链似乎不能与α链相互作用。因此，γ链似乎仅与β链相互作用，但β链能够与α链和γ链都相互作用。使用新开发的mAb通过免疫荧光检查细胞表面表达，发现静息T细胞表达低水平的γ链，而没有可检测到的α链或β链。在有丝分裂原刺激后早期，T细胞表达较高水平的α链、β链和γ链。然而，在后期时间点，T细胞表达的α链和γ链明显超过β链。因此，活化T细胞上高亲和力IL-2R的形成主要受β链表达的限制。相反，静息自然杀伤（NK）细胞组成性表达IL-2Rβ，而没有可检测到的α链或γ链。在用IL-2或IL-12激活后，α链和γ链的表达短暂增加，然后恢复到非常低的水平。因此，静息和活化NK细胞上功能性IL-2R的表达似乎主要受γ链表达的限制。对静息NK细胞的IL-2结合研究证实了免疫荧光研究的结果，表明这些细胞上存在非常少量的IL-2中等亲和力（βγ）受体。（摘要截断于四百字）
