Interleukin-2 Receptor Beta Chain Research Articles

T-lymphocyte interleukin 2-dependent tyrosine protein kinase signal transduction involves the activation of p56lck.

Addition of interleukin 2 (IL-2) to IL-2-dependent T cells results in tyrosine protein kinase signal transduction events even though the IL-2 receptor alpha and beta chains lack intrinsic enzymatic activity. Here we report that addition of IL-2 to IL-2-dependent human T cells transiently stimulates the specific activity of p56lck, a member of the src family of nonreceptor tyrosine protein kinases expressed at high levels in T lymphocytes. The ability of IL-2 to induce p56lck activation was found to be independent of the capacity of p56lck to associate with either CD4 or CD8. Following IL-2 treatment, p56lck was found to undergo serine/threonine phosphorylation modifications that resulted in altered mobility of the lck gene product on polyacrylamide gels. These observations raise the possibility that p56lck participates in IL-2-mediated signal transduction events in T cells.

Ligand-stimulated tyrosine phosphorylation of the IL-2 receptor beta chain and receptor-associated proteins.

Interleukin-2 (IL-2) stimulates the rapid phosphorylation on tyrosine of several specific cellular proteins. However, the high-affinity human IL-2 receptor, composed of an alpha (p55) and beta (p70/75) subunit, does not contain a cytoplasmic tyrosine kinase domain. In this study, we investigated the identities of the proteins phosphorylated on tyrosine in response to IL-2 stimulation to examine possible pathways of signal transduction. By the use of immunoblotting with anti-phosphotyrosine antibodies, we demonstrate that IL-2 augments tyrosine phosphorylation of the IL-2 receptor beta chain in human cell lines expressing either high-affinity (alpha/beta) receptors or only the beta chain. In IL-2-dependent mouse T cell lines, a 100,000-Da protein was phosphorylated on tyrosine in response to IL-2 and is proposed to be the mouse IL-2 receptor beta chain. Two other cellular proteins, pp55 and pp105 in human or pp55 and pp115 in mouse cell lines, were phosphorylated on tyrosine in response to IL-2 and coimmunoprecipitated with the high-affinity IL-2 receptor after chemical crosslinking of IL-2-stimulated cells. Thus, the IL-2 receptor may associate with additional subunits or with cellular proteins involved in signal transduction.

Peripheral tolerance to alloantigen results from altered regulation of the interleukin 2 pathway.

Tolerance to alloantigen may be induced in rats by administration of blood followed by transplantation of a renal allograft. The mechanism of this tolerance was investigated by directly analyzing the functional activity of graft-infiltrating cells. We have previously shown cytotoxic T lymphocyte infiltration of, and major histocompatibility complex induction on, grafts of tolerant animals. We now report that cells isolated from the grafts of tolerant rats show a reduced expression of the p55 interleukin 2 receptor (IL-2R) chain on the cell surface compared with that seen on the cells of untreated animals. Scatchard analysis further reveals low expression of high affinity IL-2R. This is due to reduced transcription of both IL-2R alpha and beta chain mRNAs and results in a reduced ability of cells to proliferate in response to IL-2. Cells isolated from tolerant animals are unable to make biologically active IL-2 in culture, whereas cells from untreated animals make high levels. This is not reflected at the mRNA level as the IL-2 gene is induced in both tolerant and untreated animals to similar levels. The induction of tolerance is abrogated by administration of recombinant IL-2 to animals at the time of transplantation. Thus, we conclude that an altered regulation of the IL-2 pathway results in tolerance in these alloantigen-treated and transplanted animals.

Growth of Certain Myeloid Leukemic Cells Can be Stimulated by Interleukin-2

The effect of recombinant interleukin-2 (IL-2) on the proliferation of T-cell depleted leukemic blasts was evaluated in 23 patients with acute myelogenous leukemia (AML). For this purpose, the effect of IL-2 on cell growth, [3H]-thymidine incorporation into the blasts and the expression of IL-2 receptors on cell surface using T-cell depleted blasts were studied. The results showed that IL-2 stimulated [3H]-thymidine incorporation significantly in blasts of 8 out of 23 cases of AML. An IL-2 induced increase in cell number was directly demonstrated in seven out of eight IL-2 responsive patients studied. IL-2 stimulated the proliferation of blasts in monocytic lineage (M4 and M5), but not all M4/M5 leukemics responded to rIL-2. Stimulation of the growth of leukemic cells was not correlated with the expression of Tac antigen on the cell surface, but it was significantly correlated with the expression of IL-2 receptor (IL-2R) beta chain on the cell surface. These results indicate that IL-2 is an active growth factor in certain myeloid leukemia cells, especially of monocytic type.

IL-4 down-regulates IL-2 receptor p75 by accelerating its endocytosis

We examined the effects of interleukin 4 (IL-4) on the expression of IL-2 receptor p75 (IL-2R p75) or beta chain on various human T cells. IL-4 promptly down-regulated surface IL-2 receptor (IL-2R) p75 in these cells. Although IL-2-induced IL-2R p75 down-regulation was seen more quickly, IL-2 did not contribute to the process of the IL-4-induced decrease of IL-2R p75. Northern blotting revealed that IL-4 did not reduce the expression of IL-2R p75 mRNA. Studies using Pronase E, which digests cell surface IL-2R p75, or brefeldin A, which blocks intracytoplasmic protein transport from endoplasmic reticulum to the Golgi apparatus, suggest that IL-4-induced IL-2R p75 down-regulation is controlled after IL-2R p75 is expressed on the cell surface. We found that IL-4 accelerated the endocytosis of IL-2R p75, which was monitored by [125I]Mik-beta 3 monoclonal antibody that recognizes non-IL-2-binding epitope on IL-2R p75. These findings demonstrate that IL-4 down-regulates IL-2R p75 mainly by accelerating its endocytosis.

Signal transduction through the human IL-2 receptor β-chain expressed in IL-6- dependent mouse B cell hybridoma

Non-covalent association between at least two polypeptides, alpha (p55) and beta (p70), yields a high-affinity interleukin 2 receptor (IL-2R). Recent findings suggest that the beta-chain can mediate IL-2 signals on its own, while the alpha-chain is not involved in IL-2 signal transduction. To study the role of the beta-chain, directly, we transfected with the human IL-2R beta-chain cDNA a murine IL-6-dependent B cell hybridoma, F12-28, which originally did not express IL-2R. We established a stable transformant, beta E12, expressing the beta-chain (Kd = 1300 pM, 3000 sites/cell) in the absence of any detectable alpha-chain. We showed that (i) beta E12 manifested the intermediate affinity IL-2 binding, which was completely blocked with anti-human beta-chain antibody (Mik-beta 1); (ii) beta E12 acquired an ability to proliferate in response to IL-2 (greater than 0.1 nM) in a dose-dependent manner. These results clearly demonstrate that the beta-chain itself is directly involved in IL-2 signal transduction in the absence of the alpha-chain. Our results also suggest that a certain IL-6-dependent B cell line possesses cellular components) capable of transducing IL-2 signals.

Identification of a soluble IL-2 receptor beta-chain from human lymphoid cell line cells.

A clone was isolated from the human lymphoid cell line YT that displayed IL-2R beta, and was found to express much higher levels of IL-2R beta than the original cells. Combining cell surface iodination, affinity labeling of the released soluble protein, and fluorescence sandwich-ELISA for both IL-2 and IL-2.(soluble)(s)IL-2R beta reactants revealed the presence of IL-2-binding protein in the culture supernatant as soluble forms of IL-2R beta. By using the fluorescence sandwich-ELISA elevated levels of sIL-2R beta were measured in culture supernatants of human T cell leukemia virus I positive T cell lines. In addition to this constitutive production of sIL-2R beta, normal PBMC could release low levels of IL-2R beta by stimulation with PHA. In contrast, this was not found in certain human T cell leukemia virus I negative T cell, B cell and macrophage lines. Immunoprecipitation of the soluble protein with IL-2R beta-specific mAb characterized it as an apparent 50- to 55-kDa molecule that is distinct from the 45-kDa soluble IL-2R alpha. Moreover, 10 to 15% of the total cell surface molecules were released into culture supernatants. These results suggest that the released IL-2R beta might serve as an immunoregulatory function in IL-2 dependent both normal and abnormal immune responses.

Increased expression of the interleukin 2 (IL-2) receptor beta chain (p70) on CD56+ natural killer cells after in vivo IL-2 therapy: p70 expression does not alone predict the level of intermediate affinity IL-2 binding.

The expression of the 70-kD beta subunit of the interleukin 2 receptor (IL-2R) has been examined on peripheral blood lymphocytes (PBL) obtained from patients receiving systemic infusions of IL-2. Using monoclonal antibodies directed against p70, flow cytometric analyses revealed a greater than threefold increase in expression of the IL-2R beta chain on CD56+ natural killer (NK) cells from post-IL-2 therapy PBL relative to pre-therapy cells. The level of p70 expression on the post-therapy cells was three- to fourfold greater (based on fluorescence intensity) than the level of p70 expression on YT cells, an NK-like cell line that expresses approximately 12,000 intermediate affinity IL-2 binding sites/cell. Despite the high level of p70 expression, in 125I-IL-2 binding assays only 790-1,290 intermediate affinity IL-2 binding sites/cell were detected on post-therapy cells from six patients. These data represent the first report of increased p70 expression after in vivo IL-2 administration and suggest a requirement for at least one additional subunit for the formation of functional intermediate affinity IL-2Rs. Furthermore, the presence on the surface of post-therapy NK cells of excess p70 that does not bind IL-2 with intermediate affinity implies that the formation of intermediate affinity IL-2Rs is not solely determined by the level of p70 expression, and that the response of NK cells to IL-2 might be regulated by altering the expression of p70 or some other IL-2R subunit.

Interleukin-2 receptor beta-chain (p70-75) expressed on leukemic cells from adult T cell leukemia patients.

To determine whether the interleukin‐2 receptor (IL‐2R) β‐chain (p70–75) is expressed on lenkemic cells from patients with adult T cell leukemia (ATL) as well as α‐chain (p55, Tac), we performed radiolabeled interleukin‐2 (IL‐2) binding assay, chemical crosslinking of radiolabeled IL‐2 and flow cytometric analysis using a newly‐developed anti‐IL‐2R β‐chain antibody. The results showed that leukemic cells from all the 12 ATL patients we examined expressed the IL‐2R β‐chain together with the α‐chain, whereas there was no detectable β‐chain expression on unstimulated peripheral blood CD4(+) T cells from healthy volunteers. Southern blot analysis revealed that this abnormal expression was not caused by the structural change of IL‐2R β‐chain gene. Though leukemic cells from all ATL patients examined expressed high‐affinity IL‐2Rs, leukemic cells from only 25% of all ATL patients proliferated in response to IL‐2. These results showing abnormal expression of IL‐2R β‐chain on leukemic cells from ATL patients (ATL cells) suggest a close association between HTLV‐I infection and abnormal β‐chain expression as well as α‐chain expression.

Interleukin 2 receptor beta chain expressed in an oligodendroglioma line binds interleukin 2 and delivers growth signal.

Interleukin 2 (IL-2) is a potent growth factor for T lymphocytes, playing a crucial role in the immune response. In view of the considerable evidence that the immunoregulatory cytokines (or lymphokines) also play a role in the growth and differentiation of cells in the central nervous system (CNS), we examined the operation of the IL-2 system in a cell line of CNS origin by expressing a cDNA encoding the beta chain of the human IL-2 receptor (IL-2R beta, a 75-kDa protein). When the cDNA was expressed in a human oligodendroglioma cell line, ONS-21, the IL-2R beta bound IL-2 with an affinity similar to that in lymphoid cells (Kd, approximately 2 nM). Furthermore, cell proliferation ([3H]thymidine incorporation) was stimulated by IL-2. These results demonstrate that the same cytokine receptor is functional in cells of the immune system and CNS and point to a molecular mechanism that is similar for growth-signal transduction between lymphoid and neural cells but that may be different in other cells, such as fibroblasts.

Flow cytometric analysis of expression of interleukin-2 receptor beta chain (p70-75) on various leukemic cells

We analyzed the expression of the interleukin-2 receptor (IL-2R) beta chain (p70–75) on various leukemic cells from 44 patients by flow cytometric analysis using the IL-2R beta chain-specific monoclonal antibody (MoAb), designated Mik-beta 1, which has been recently developed. Flow cytometric analysis demonstrated the expression of the IL-2R beta chain on granular lymphocytes (GLs) from all eight patients with granular lymphocyte proliferative disorders (GLPDs), on adult T- cell leukemia (ATL) cells from all three patients with ATL, and on T- cell acute lymphoblastic leukemia (T-ALL) cells from one of three patients with T-ALL. Although GLs from all the GLPD patients expressed the IL-2R beta chain alone and not the IL-2R alpha chain (Tac-antigen: p55), ATL and T-ALL cells expressing the beta chain coexpressed the alpha chain. In two of seven patients with common ALL (cALL) and in both patients with B-cell chronic lymphocytic leukemia, the leukemic cells expressed the alpha chain alone. Neither the alpha chain nor the beta chain was expressed on leukemic cells from the remaining 28 patients, including all 18 patients with acute nonlymphocytic leukemia, five of seven patients with cALL, all three patients with multiple myeloma, and two of three patients with T-ALL. These results indicate that three different forms of IL-2R chain expression exist on leukemic cells: the alpha chain alone; the beta chain alone; and both the alpha and beta chains. To examine whether the results obtained by flow cytometric analysis actually reflect functional aspects of the expressed IL-2Rs, we studied the specific binding of 125I-labeled IL-2 (125I-IL-2) to leukemic cells in 18 of the 44 patients. In addition, we performed 125I-IL-2 crosslinking studies in seven patients. The results of IL-2R expression of both 125I-IL-2 binding assay and crosslinking studies were in agreement with those obtained by flow cytometric analysis. These results indicate that flow cytometric analysis using MoAbs, anti-Tac, and Mik-beta 1 is useful for detecting the expression of the IL-2R chains.

Flow Cytometric Analysis of Expression of Interleukin-2 Receptor β Chain (p70-75) on Various Leukemic Cells

We analyzed the expression of the interleukin-2 receptor (IL-2R) beta chain (p70-75) on various leukemic cells from 44 patients by flow cytometric analysis using the IL-2R beta chain-specific monoclonal antibody (MoAb), designated Mik-beta 1, which has been recently developed. Flow cytometric analysis demonstrated the expression of the IL-2R beta chain on granular lymphocytes (GLs) from all eight patients with granular lymphocyte proliferative disorders (GLPDs), on adult T-cell leukemia (ATL) cells from all three patients with ATL, and on T-cell acute lymphoblastic leukemia (T-ALL) cells from one of three patients with T-ALL. Although GLs from all the GLPD patients expressed the IL-2R beta chain alone and not the IL-2R alpha chain (Tac-antigen: p55), ATL and T-ALL cells expressing the beta chain coexpressed the alpha chain. In two of seven patients with common ALL (cALL) and in both patients with B-cell chronic lymphocytic leukemia, the leukemic cells expressed the alpha chain alone. Neither the alpha chain nor the beta chain was expressed on leukemic cells from the remaining 28 patients, including all 18 patients with acute nonlymphocytic leukemia, five of seven patients with cALL, all three patients with multiple myeloma, and two of three patients with T-ALL. These results indicate that three different forms of IL-2R chain expression exist on leukemic cells: the alpha chain alone; the beta chain alone; and both the alpha and beta chains. To examine whether the results obtained by flow cytometric analysis actually reflect functional aspects of the expressed IL-2Rs, we studied the specific binding of 125I-labeled IL-2 (125I-IL-2) to leukemic cells in 18 of the 44 patients. In addition, we performed 125I-IL-2 crosslinking studies in seven patients. The results of IL-2R expression of both 125I-IL-2 binding assay and crosslinking studies were in agreement with those obtained by flow cytometric analysis. These results indicate that flow cytometric analysis using MoAbs, anti-Tac, and Mik-beta 1 is useful for detecting the expression of the IL-2R chains.

The IL-2 receptor beta-chain (p70). Ligand binding ability of the cDNA-encoding membrane and secreted forms.

The high affinity IL-2R is composed of at least two distinct subunits; alpha (p55 or Tac)- and beta (p70)-chains. Recent cDNA expression studies with lymphoid cells unequivocally demonstrated that the IL-2R beta is an indispensable component for the ligand internalization and the signal transduction via the high affinity IL-2R. Furthermore, these studies confirmed that the IL-2R beta singly expressed on T lymphoid cells represents the intermediate affinity IL-2R. In the present study, however, we show 1) the IL-2R beta expressed on a mouse fibroblast line, NIH-3T3, did not bind IL-2 under the intermediate affinity conditions, 2) nevertheless, the IL-2R beta coexpressed with the IL-2R alpha not only formed the high affinity receptor but also internalized IL-2. By the use of competitive sandwich ELISA to study the IL-2 binding ability of the IL-2R beta molecule itself, we also show that the IL-2R beta present in the detergent-solubilized cell extracts and the secreted IL-2R beta (p37) produced by the truncated cDNA are actually capable of binding IL-2, but with a much reduced affinity compared with the intact IL-2R beta expressed on the lymphoid cells. These findings lead us to postulate a more complex feature of the IL-2R than ever speculated; the IL-2R beta molecule having on its own minimal IL-2 binding ability requires a putative gamma-chain specifically present on lymphoid cells to generate the functional intermediate affinity IL-2R. The gamma-chain, however, seems not to be required as far as the formation of the high affinity IL-2R by the alpha- and beta-chains and the ligand internalization through it are concerned.

A PHASE I-II STUDY EVALUATING THE MURINE ANTI-IL-2 RECEPTOR ANTIBODY 2A3 FOR TREATMENT OF ACUTE GRAFT-VERSUS-HOST DISEASE

A murine IgG1 antibody specific for the IL-2-binding site on the human lymphocyte IL-2 receptor beta chain (CD25) was evaluated in 11 patients who developed acute graft-versus-host disease following allogeneic marrow transplantation. All patients had received cyclosporine and methotrexate for prophylaxis of GVHD, either alone (4 cases), or in combination with antithymocyte globulin (4 cases) or with prednisone (3 cases). Patients had developed GVHD at 7-53 days (median 12) after transplantation and had failed treatment with corticosteroids for 3-44 days (median 19). Residual GVHD was of grade II severity in 4 patients, grade III in 5 patients, and grade IV in 2 patients. Sequential patients received monoclonal antibody in escalating doses from 0.1 mg/kg/day to 1.0 mg/kg/day for 7 days. Side effects were fever, respiratory distress, hypertension, hypotension, and chills occurring in 11 of 72 (14%) antibody infusions. Trough antibody levels greater than 6 micrograms/ml were achieved in patients treated with 0.5 or 1.0 mg/kg/day. Four of eight evaluable patients had an IgM antibody response, and one had an IgG response to the murine immunoglobulin. Clinical response of GVHD was evaluated in 10 patients who received the entire course of the antibody treatment. Among 7 patients treated within 40 days from transplantation, one patient had a complete response in the skin as the only involved organ, and 3 patients had a partial response, 2 in the skin and one in the gastrointestinal tract. No responses were achieved with liver disease at anytime or in any organ in patients treated beyond 40 days after transplantation. Since administration of this antibody was well tolerated and some efficacy was observed in patients with acute GVHD treated early after transplantation, there is a rationale for testing this antibody as an agent for prophylaxis of GVHD.

Expression of murine IL-2 receptor beta-chain on thymic and splenic lymphocyte subpopulations as revealed by the IL-2-induced proliferative response in human IL-2 receptor alpha-chain transgenic mice.

Lymphocytes from the human (h) IL-2R alpha chain transgenic mice (TGM) constitutively express high affinity binding sites for hIL-2, consisting of transgenic h-IL-2R alpha and endogenous murine IL-2R beta, and therefore easily proliferate in vitro in response to hIL-2. Our study was undertaken to clarify the hIL-2-responsive lymphocyte subsets in the TGM, which should most likely reflect the normal distribution of m IL-2R beta expression. In both thymus and spleen, the majority of expanded cells by hIL-2 was CD3+CD4-CD8+ TCR alpha beta+ cells. The proliferation of CD4+ cells was not observed at all from either organ despite the expression of transgenic hIL-2R alpha. Potent cellular proliferation was also observed from the thymocytes that had been depleted of CD8+ cells, the expanded cells consisting of CD3- (15-40%) and CD3+ populations (60-85%). Among CD3+ cells, approximately the half portion expressed TCR alpha beta, whereas the other half was suggested to express TCR gamma delta. A variable portion (5-20%) of the CD3+ cells expressed CD8 (Lyt-2) in the absence of Lyt-3, and the CD3+CD8+ cells were confined preferentially to the TCR alpha beta- (TCR gamma delta+) population. In the culture of splenocytes depleted of CD8+ cells, however, the proliferated cells were mostly CD3-CD4-CD8-TCR-Mac1-, whereas a minor portion (10-30%) was CD3+CD4-CD8-TCR alpha beta- (TCR gamma delta+. Analysis of TCR genes at both DNA and mRNA levels confirmed the phenotypical observations. These results strongly suggested that IL-2R beta was constitutively and selectively expressed on the primary murine thymocytes and splenic T and NK cells, except for CD4+ cells in both organs.

Human interleukin 2 receptor beta-chain gene: chromosomal localization and identification of 5' regulatory sequences.

Interleukin 2 (IL-2) binds to and stimulates activated T cells through high-affinity IL-2 receptors (IL-2Rs). Such receptors represent a complex consisting of at least two proteins, the 55-kDa IL-2R alpha chain and the 70-kDa IL-2R beta chain. The low-affinity, IL-2R alpha chain cannot by itself transduce a mitogenic signal, whereas IL-2 stimulates resting lymphocytes through the intermediate-affinity, IL-2R beta receptor. We report here identification of the genomic locus for IL-2R beta. The exons are contained on four EcoRI fragments of 1.1, 9.2, 7.2, and 13.7 kilobases. The 1.1-kilobase EcoRI fragment lies at the 5'-most end of the genomic locus and contains promoter sequences. The promoter contains no TATA box-like elements but does contain the d(GT)n class of middle repetitive elements, which may play an interesting regulatory role. The IL-2R beta gene is localized to chromosome 22q11.2-q12, a region that is the locus for several lymphoid neoplasias.

Differential expression of the interleukin 2 receptor β (p75) chain on human peripheral blood natural killer subsets

The interleukin-2 receptor (IL-2R) is composed of at least two subunits, the IL-2R alpha (P55, CD25/Tac) and IL-2R beta (p70-75) chains. In the present study we have identified the quantitative expression of IL-2R beta on subsets of NK cells in peripheral blood using flow cytometry and a recently established mAb against IL-2R beta (TU27). We demonstrate that NK cells are not a homogeneous population but that phenotypic subsets exist, and that the levels of IL-2R beta expression correlate with these subsets. The levels of IL-2R beta expression on NK subsets are CD3- CD16- CD56bright NK cells (immature NK) greater than CD16+CD4- NK cells (mature NK) greater than CD16+CD57+ NK cells (more mature NK) in adult peripheral blood lymphocytes. The level of IL-2R beta expression on CD16+ NK cells in cord blood is significantly higher than that in adult PBL. These findings suggest that there may be a inverse relationship between IL-2R beta expression and the differentiation of NK cells. IL-2R beta, preferentially expressed on the NK cells, may play an important role in differentiation and maturation of NK cells.

An associated molecule, p64, eith high-affinity interleukin 2 receptor

TU11 mAb specific for the human interleukin-2 receptor (IL-2R) beta-chain, p75, co-precipitated two molecules, p64 and p55, with the beta-chain in the lysates of cells bearing the high-affinity IL-2R. The co-precipitation was detected in the presence of IL-2 even in the absence of a chemical cross-linker. H-48 mAb specific for the IL-2R alpha-chain completely pre-absorbed p64 as well as p55 and partially pre-absorbed the beta-chain from the lysates. The co-precipitation was also detected in phytohemagglutinin-stimulated normal peripheral blood lymphocytes, which express the high-affinity IL-2R, but not in the cell line cells bearing only the low-affinity IL-2R. The peptide maps indicate that p64 is a molecule distinct from both the alpha- and beta-chains, and that p55 is identical to the alpha-chain. These findings suggest that p64, along with the alpha- and beta-chains, is a component of the high affinity IL-2R complex, and we have tentatively named it the gamma-chain of IL-2R.

The human interleukin-2 receptor β-chain gene: genomic organization, promoter analysis and chromosomal assignment

The chromosomal gene for the human interleukin-2 receptor beta-chain (IL-2R beta) was isolated and characterized. The entire IL-2R beta gene is composed of ten exons spanning about 24.3 kilobases, in which the protein is encoded by the exons 2-10. The cysteine rich extracellular region which displays a significant evolutionary resemblance to other cytokine receptors, as well as growth hormone and prolactin receptors, is encoded primarily by exons 3 and 4, whereas the membrane proximal, cysteine poor domain showing a homology with type III modules of fibronectin is encoded by exon 7. Sequence analysis of the 5'-flanking region revealed the presence of potential binding sites for transcription factors such as Octamer binding factors, AP-1, AP-2 as well as the 'GC-clusters'. At least five potential cap sites were identified by S1 mapping analysis. The 850 bp DNA sequence of the 5'-flanking region exhibited constitutive promoter activity when it was linked upstream of the HSV-tk reporter gene and then transfected into YT cells, a human leukemic cell line. By applying the RFLP linkage analysis, the IL-2R beta gene has been assigned to chromosome 22q12-13.

Selective inhibition of high- but not low-affinity interleukin 2 binding by lectins and anti-interleukin 2 receptor alpha antibody.

The present study demonstrated that various reagents can specifically reduce the affinity of high-affinity interleukin 2 receptor (IL-2R) but not that of low-affinity IL-2R. They included lectins such as wheat germ agglutinin (WGA), concanavalin A and phytohemagglutinin, and a chemical cross-linker, glutaraldehyde, in addition to anti-IL-2R monoclonal antibodies, HIEI and H-47. The affinity of the high-affinity IL-2R was reduced when the cells were treated with WGA or H-47 before, but not after, addition of 125I-labeled interleukin 2 (IL-2). Their inhibitory effects were also demonstrated by the chemical cross-linking method. On treatment with the reagents, the IL-2 binding to both IL-2R alpha and beta chains was inhibited and these inhibitory effects were seen only when the reagents were added before IL-2 addition, like their high-affinity reducing effects. These results support a supposition that the high affinity IL-2R is generated by assembly of the alpha and beta chains, and suggest that the IL-2 binding to IL-2R alpha and beta chains could induce stable constitution of the high-affinity state of IL-2R, but these affinity modulating reagents could perturb the optimum association between alpha and beta chains to generate the high-affinity IL-2R.