Biomedical subjects

M Tsudo

Publications and source records attributed to M Tsudo.

At least 37 records · Page 2Linked to original sources

PubMed1992

The third molecule associated with interleukin 2 receptor alpha and beta chain.

It is known that the affinity cross-linking study of the human high-affinity Interleukin 2 (IL-2) receptor reveals triplet bands consisting of 70 kDa alpha chain(Tac)-IL-2 and the 90/80 kDa doublet. We found the cell lines lacking the lower band of the doublet in spite of the expression of both alpha and beta chains. No IL-2 binding was detectable in the presence of anti-Tac antibody in these cells. Immunoprecipitation from the cell extract of [125 I] IL-2-cross-linked T cells with anti-beta chain polyclonal IgG detected the upper band, but not lower band of the doublet. These data suggest that the lower band of the doublet represents an unknown IL-2-binding protein (p65) distinct from the beta chain and this molecule may be involved in the intermediate-affinity IL-2 binding together with the beta chain.

3T3 Cells↗

PubMed1992

The interleukin 2 receptor (IL-2R): the IL-2R alpha subunit alters the function of the IL-2R beta subunit to enhance IL-2 binding and signaling by mechanisms that do not require binding of IL-2 to IL-2R alpha subunit.

Interleukin 2 (IL-2)-mediated signaling through its high-affinity receptor involves a complex interrelationship between IL-2 and two IL-2-binding chains, IL-2R alpha and beta chains. Previously with the reagents available it was difficult to define functional interactions between these two IL-2R subunits involved in IL-2 binding and signal transduction. To extend our understanding of the interplay between the two binding subunits we have done studies with the monoclonal antibody HIEI, which interferes with interaction of IL-2R alpha and beta chains (IL-2R alpha and IL-2R beta, respectively). Furthermore, we used two forms of IL-2, recombinant native IL-2 and F42A, an IL-2 analog (Phe-42----Ala substitution) that binds only to IL-2R beta. Analog F42A manifested 75-100% of the bioactivity of wild-type IL-2. This observation is inconsistent with the strict hierarchical IL-2-binding affinity conversion model previously proposed by Saito and coworkers [Saito Y., Sabe, H., Suzuki, N., Kondo, S., Ogura, T., Shimizu, A. & Honjo, T. (1988) J. Exp. Med. 168, 1563-1572] that predicted an ordered sequence of events in which IL-2 must first bind to IL-2R alpha before its interaction with IL-2R beta. Previous investigations using IL-2 variants were interpreted to show that IL-2R alpha merely acts to concentrate IL-2 to the cell surface and that no other meaningful interaction occurred between IL-2R alpha and IL-2R beta. However, our data are inconsistent with this view. We draw this conclusion on the basis of our observation that antibody HIEI, which reacts with an epitope of IL-2R alpha and interferes with interaction of this chain and IL-2R beta, inhibits the IL-2-dependent proliferative effects mediated by analog F42A. Furthermore, by blocking interaction of IL-2R alpha and IL-2R beta with the antibody HIEI, a decrease in the affinity of radiolabeled analog F42A for IL-2R beta was seen. In our proposed model IL-2R alpha contributes several functions to IL-2-mediated signaling through the high-affinity IL-2R. These functions include concentration of IL-2 within the two-dimensional surface of the plasma membrane as well as alteration of the functional capacity of IL-2R beta, an effect that does not require prior binding of IL-2R to IL-2R alpha. The IL-2R alpha-mediated augmentation of IL-2R beta functions involves affinity conversion of IL-2R beta, increasing its affinity for IL-2, and may involve facilitation of Il-2-mediated signaling after binding of IL-2 to this IL-2R beta.

Amino Acid Sequence↗

PubMed1991

A novel monoclonal antibody against murine IL-2 receptor beta-chain. Characterization of receptor expression in normal lymphoid cells and EL-4 cells.

A mAb specific for the murine IL-2R beta-chain (IL-2R beta) was produced by immunizing a rat with a rat transfectant cell line expressing a large number of cDNA-encoded murine IL-2R beta. The mAb, designated TM-beta 1, is specifically reactive with the murine IL-2R beta cDNA-transfectant but not with the recipient cell, and immunoprecipitates murine IL-2R beta of Mr 75 to 85 kDa. TM-beta 1 mAb completely abolished the high affinity IL-2 binding by inhibiting the ligand binding to IL-2R beta. Murine IL-2R beta was found to be constitutively expressed on a subpopulation of CD8+ T cells and almost all NK1.1+ NK cells in the spleen, whereas TM-beta 1 mAb inhibited the proliferation of spleen cells induced by 1 nM of IL-2. Interestingly, EL-4 cells that express murine IL-2R beta as detected by TM-beta 1 mAb can bind neither human nor murine IL-2 under the intermediate affinity conditions, although cDNA-directed human IL-2R beta expressed in the same EL-4 cells has been previously shown to manifest the intermediate affinity IL-2 binding. These results may imply that functional expression of IL-2R beta is differentially regulated between humans and mice. Finally, our neutralizing anti-IL-2R beta mAb TM-beta 1 will be useful not only for various in vitro studies but also for in vivo studies to directly investigate the possible involvement of the IL-2/IL-2R pathway in the generation and differentiation of T lymphocytes and NK cells.

Animals↗

PubMed1991

Interleukin-2 receptor regulates activation of phosphatidylinositol 3-kinase.

Interleukin-2 (IL-2) stimulates proliferation of T lymphocytes and is involved in the activation of both natural killer and lymphokine-activated killer precursor cells. The intracellular messengers which mediate IL-2-dependent events have not yet been identified. IL-2 receptor is not a protein-tyrosine kinase. Activation of a cellular protein-tyrosine kinase and direct association of a protein-tyrosine kinase activity with the IL-2 receptor occurs within minutes of IL-2 stimulation. We investigated the activation of phosphatidylinositol 3-kinase (PI 3-kinase) in IL-2-mediated signal transduction using the IL-2-dependent murine T-cell line, CTLL-2, and human phytohemagglutinin-stimulated peripheral blood lymphocytes (phytohemagglutinin blasts). Within a minute following stimulation of these cells with IL-2, PI 3-kinase activity could be detected in antiphosphotyrosine (anti-P-Tyr) antibody immunoprecipitates. IL-2 triggered a direct association of PI 3-kinase with the IL-2 receptor as detected in immunoprecipitates using anti-IL-2 receptor beta chain antibody. In vivo labeled CTLL-2 cells have a time-dependent increase in D-3-phosphorylated polyphosphoinositides following stimulation with IL-2. This is the first group of second messengers identified in IL-2-mediated signal transduction.

1-Phosphatidylinositol 4-Kinase↗

PubMed1991

Functional p75 interleukin-2 receptor expression on the fresh blast cells in childhood acute lymphoblastic leukemia with natural killer cell properties.

Neoplastic cells of childhood acute lymphoblastic leukemia (ALL) with natural killer (NK) cell properties were studied for the expression of p75 interleukin-2 receptors (IL-2R) and the receptor functions. Freshly prepared blast cells from a patient with ALL had NK cell properties: (1) the phenotype such as CD56+, CD2+, E-rosette+, CD3-, and CD19-; and (2) the presence of spontaneous cytotoxicity against NK-sensitive K562 target cells. Although p55 Tac antigen was not detectable, there was the expression of p75 IL-2R on the freshly prepared blast cells: 70% of the cells reacted with Mik-beta 1 monoclonal antibody against p75 IL-2R as determined by flow cytometry. Two-color flow cytometry revealed that the blast cells expressed both p75 IL-2R and NKH-1. NK activity of the blast cells was augmented by their treatment with 1,000 U/ml recombinant IL-2 (rIL-2): the cytotoxicity level as percentage lysis increased to 38.7% from 22.0% when the normal lymphocyte value increased to 62.1% from 46.2%. Although the blast cells possessed no apparent level of proliferative capacity, the addition of 1,000 U/ml rIL-2 yielded a 2.7-fold increase in their thymidine uptake. These results demonstrate the expression of functional p75 IL-2R on the patient's blast cells with NK cell properties.

Adolescent↗

PubMed1991

Impaired expression of interleukin 2 receptors in childhood acute lymphoblastic leukemia.

Peripheral blood mononuclear cells (PBMC) from acute lymphoblastic leukemia (ALL) patients were studied for the expression of interleukin 2 receptors (IL-2R). When stimulated with phytohemagglutinin (PHA) for 3 days, the percentage of p55 Tac positive cells and the number of high affinity IL-2R was decreased in on-therapy ALL patients at remission and returned to normal after cessation of the treatment. However, the percentage of p75 IL-2R positive PBMC was normal in all ALL patients at remission. It is well-known that there are several immunological abnormalities including T and natural killer (NK) cell dysfunctions in ALL patients undergoing maintenance chemotherapy. IL-2 facilitates T-cell growth and corrects defective NK activity. Taking this into account, there may be a poor utilization of autologously produced IL-2 because of the impaired expression of IL-2R, and this poor utilization of IL-2 may be related to the defective immunological functions in childhood ALL patients at remission who are receiving maintenance chemotherapy.

Adolescent↗

PubMed1991

Signal transduction through the human IL-2 receptor beta-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.

Animals↗

PubMed1991

Regulatory mechanisms for the expression of a functional beta chain of interleukin 2 receptor on T4 chronic lymphocytic leukemia cells.

Monoclonal antibodies, each recognizing interleukin 2 receptor (IL-2R) alpha, or beta, were used to see the regulatory mechanisms of the expressions on leukemic cells from a patient with T4 chronic lymphocytic leukemia (T4-CLL). Cells from this patient expressed only IL-2R beta, and the expression was enhanced by medium cultivation. IL-1 enhanced the expression of not only IL-2R beta but also IL-2R alpha on the cells. Binding studies using 125I-IL-2 showed the presence of an intermediate receptor (734 sites/cell, Kd = 1.2 nM) and a few high-affinity receptor (172 sites/cell, Kd = 132 pM) on cells cultured with IL-1. IL-2 and IL-1 synergistically promoted the proliferation of the cells, suggesting that the induced IL-2R was functional. In addition, anti-IL-1 antibodies inhibited IL-2R beta expression by cultured cells, suggesting that it was dependent on IL-1 produced by the leukemic cells. These findings suggested that IL-1 might enhance the expression of IL-2R beta in a subset of human T cells, and implied a role of IL-1 in the proliferation of the leukemic T cells.

Aged↗

PubMed1990

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.

Antibodies, Monoclonal↗

PubMed1990

IL-4 inhibits the expression of high affinity IL-2 receptors on monoclonal human B cells.

In the presence of anti-mu antibodies (anti-microAb), monoclonal B lymphocytes from patients suffering from B type chronic lymphocytic leukemia (B-CLL) can respond to IL-2. In contrast to the effect it exerts on normal B cells, IL-4 does not promote DNA synthesis by B-CLL lymphocytes. Rather this interleukin inhibits the response to IL-2 in all patients' cells that responded to this interleukin. We thus examined whether IL-4 would modulate the number and/or the affinity of IL-2 receptors. A 3-day activation of cells by anti-microAb induced a few hundred high affinity IL-2 receptors (HA-IL-2R) on B-CLL cell surface, as determined by Scatchard analysis. Treatment of cells with IL-4 caused a marked decrease in the number of HA-IL-2R without interfering with the binding ability of IL-2. In contrast with this profound suppressive effect, IL-4 did not down-regulate the expression of each chain, alpha and beta (p55 and p75, respectively), of the HA-IL-2R heterodimer. In fact, the expression of alpha and beta induced by anti-microAb was enhanced by IL-4. Altogether, IL-4 exerts a critical influence on the function and the configuration of HA-IL-2R without inhibiting the expression of two subunits, alpha and beta.

B-Lymphocytes↗

PubMed1990

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.

Antibodies, Monoclonal↗

PubMed1990

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.

Amino Acid Sequence↗

PubMed1990

Human B lymphocytes express the p75 component of the interleukin 2 receptor.

The nature of the interleukin 2 (IL-2) receptor on purified human B lymphocytes was examined. Both normal and malignant cells showed evidence of a 70-75,000 mol. wt (p75) IL-2 binding molecule as assessed by 125I-labeled IL-2 binding and receptor cross-linking. On normal, Tac-negative B lymphocytes the estimated number of p75 binding sites was 1100 per cell and the dissociation constant (Kd) was 1.7 nM. Consistent with this, cross-linking experiments demonstrated the presence of an IL-2 binding molecule of 70-75,000 mol. wt. Purified B cells from patients with hairy cell leukemia and chronic lymphocytic leukemia (CLL) also expressed the p75 IL-2 binding molecule. In the HCL samples, a small number of high-affinity IL-2 binding sites were detected (27-90) while the majority of binding sites (2100-10,800) were typical of low-affinity p55 Tac binding. IL-2 added to the purified normal and CLL B lymphocytes led to the induction of p55 Tac expression and the generation of high-affinity IL-2 receptors. This response to IL-2 was equivalent to the response observed when normal B lymphocytes were stimulated by Staphylococcus aureus Cowan I.

Antigens, CD↗

PubMed1990

Accessory cell-derived helper signals in human T-cell activation with phytohemagglutinin: induction of interleukin 2-responsiveness by interleukin 6, and production of interleukin 2 by interleukin 1 [corrected].

Interleukins (IL-) 1 and 6 have been shown to represent accessory signals for T-cell activation. In the present study, we further examined the effects of both cytokines on accessory cell-depleted human T cells stimulated with phytohemagglutinin (PHA). The addition of IL-6 to the cultures resulted in T-cell proliferation; however, IL-1 was unable to support PHA-induced T-cell growth. The addition of IL-1 consistently induced a low level of IL-2 production and strongly enhanced T-cell proliferation in the presence of IL-6. Thus, the effect of IL-1 on T-cell growth becomes apparent only in the presence of IL-6. Blocking the IL-2-receptor (IL-2R) with the monoclonal antibodies anti-Tac and MikBêta 1 (directed to the alpha and bêta chains of the IL-2R, respectively) had no effect on PHA/IL-6-supported proliferation, but completely eliminated the growth-enhancing effect of IL-1. On the other hand, a neutralizing anti-IL-4-antiserum did not affect PHA/IL-6- or PHA/IL-6/IL-1-induced proliferation. Further experiments showed that IL-6 enhances T-cell responsiveness to IL-2, as evidenced by enhanced IL-2-induced proliferation. However, we could not find an effect of IL-6 on the expression of IL-2R as measured by staining with anti-Tac and with MikBêta 1 or by binding of (125I)-IL-2 to T cells. It can be concluded from these studies that IL-1 and IL-6 have different helper effects on PHA-induced T-cell activation. In the presence of PHA, IL-6 induces limited IL-2/IL-4-independent growth, and more importantly it renders T cells responsive to IL-2. IL-1 provides a signal leading to IL-2 production. The combination of IL-1 and IL-6 represents a synergistic helper signal, leading to an IL-2-dependent pathway of proliferation.

Antigen-Presenting Cells↗

PubMed1990

Expression of the p70 chain of the IL-2 receptor on human lymphoid cells: analysis using a monoclonal antibody and high-sensitivity immunofluorescence.

Using monoclonal antibody (MoAb) against the p70 (beta) chain of the interleukin-2 receptor (IL-2R) and a high-sensitivity immunofluorescence procedure, p70 can be demonstrated on the majority of lymphocytes from normal blood samples, without in vitro stimulation. A subpopulation of cells bears a high concentration of receptor, and these cells have the physical properties of large granular leucocytes (LGL). The smaller lymphocytes, although weaker, are quite clearly positive. T8 cells stain relatively strongly, while T4 cells and B cells stain relatively weakly. Leukaemic cells showed a variety of phenotypes when examined for expression of the p55 and p70 chains of the IL-2R. The demonstration of IL-2R chains directly by immunofluorescence on unstimulated lymphocytes has potential clinical applications, since this technique can be used in a diagnostic setting.

Antibodies, Monoclonal↗

PubMed1990

Murine interleukin 2 receptor beta chain: dysregulated gene expression in lymphoma line EL-4 caused by a promoter insertion.

The functional, high-affinity interleukin 2 receptor (IL-2R) consists of at least two receptor components, IL-2R alpha (p55) and IL-2R beta (p70-75). The cDNA encoding the murine IL-2R beta has been isolated by using the previously cloned cDNA for human IL-2R beta as a probe. Analysis of the cDNA revealed that the murine IL-2R beta shows a marked homology with the human IL-2R beta and that it is also structurally related to other cytokine receptors such as erythropoietin receptor. The cDNA-directed murine IL-2R beta formed high-affinity IL-2R in conjunction with the endogenous IL-2R alpha in a murine pro-B-cell line and could transduce IL-2-induced growth signal. In mouse lymphoma line EL-4, the IL-2R beta gene was found to be rearranged by the insertion of the long terminal repeat sequence of an intracisternal A particle, giving rise to constitutive expression of the IL-2R beta mRNA.

Amino Acid Sequence↗

PubMed1990

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) beta-chain (p70-75) is expressed on leukemic cells from patients with adult T cell leukemia (ATL) as well as alpha-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 beta-chain antibody. The results showed that leukemic cells from all the 12 ATL patients we examined expressed the IL-2R beta-chain together with the alpha-chain whereas there was no detectable beta-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 beta-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 beta-chain on leukemic cells from ATL patients (ATL cells) suggest a close association between HTLV-I infection and abnormal beta-chain expression as well as alpha-chain expression.

Aged↗

PubMed1990

IL-2 receptors on rabbit T-cell lines and their transfectants expressing the human IL-2 receptor alpha chain.

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.

Animals↗