IL-2R Alpha Chain Research Articles

T-Cell Development in Human Thymoma

Human thymoma is derived from thymic epithelial cells and often associated with a large number of cortical thymocytes. Since thymic epithelial cells play key roles in T-cell development in the normal thymus, we hypothesized that the neoplastic epithelial cells of thymoma may support T-cell differentiation. We attempted to reconstitute the T-cell development in vitro by using neoplastic epithelial cells isolated from thymoma. CD34, a stem cell marker, was expressed on a proportion of CD4-CD8- cells in thymoma. These CD34+CD4-CD8- cells also expressed both IL-7R alpha-chain and common gamma-chain. Purified CD4-CD8- cells from thymomas were cultured with the neoplastic epithelial cells, and their differentiation into CD4+CD8+ cells via CD4 single positive intermediates was observed within 9 days' co-culture in the presence of recombinant IL-7. The CD34+CD4-CD8- cells purified from a normal thymus also differentiated to CD4+CD8+ cells in an allogeneic co-culture with the neoplastic epithelial cells of thymoma. In addition, a pleural dissemination from thymoma contained a large amount of cortical thymocytes. These results suggest that the neoplastic epithelial cells retain the function of thymic epithelium and can support T-cell development in thymomas.

Defective IL-2 receptor expression in lymphocytes of patients with arsenic-induced Bowen's disease.

The immune function of peripheral mononuclear cells (MNC) in patients with endemic arsenic-induced Bowen's disease (BD) was investigated. Many cytokines and immune-related factors were determined in the present study. Interleukin-1beta and TNF-alpha production was used as an indicator of monocyte/macrophage function. II-2 and sIL-2R production was used as an indicator of lymphocyte activation. The release of sCD4 and sCD8 was used as an indicator of activation of respective T-cell subpopulations. Production of IFN-gamma and IL-2 reflected the cellular effector function of helper T-cells type 1. In vivo cell-mediated immunity was also assessed by estimation of the percentage of T-cells in peripheral blood MNC and the nonspecific delayed-type hypersensitivity (DTH) response to 2,4-dinitrochlorobenzene (DNCB). Both assays revealed depressed cell-mediated immunity in BD. Compared with healthy controls, spontaneous and PHA-induced IFN-gamma and TNF-alpha production was significantly decreased in BD whereas spontaneous release of IL-2, sCD4 and sCD8 was significantly increased. Although PHA stimulation increased IL-2 release, the expression of IL-2R alpha and beta chains and the release of sIL-2R were not proportionately increased in BD. In addition, IL-2-mediated [3H]-thymidine incorporation by MNC in patients with BD was significantly decreased. These findings suggest that the defective cell-mediated immune function in BD is due to impairment of membrane IL-2R expression in lymphocytes after stimulation.

Interaction affinity between cytokine receptor components on the cell surface.

The anti-common gamma chain (gammac) mAb CP.B8 is shown to inhibit interleukin 4 (IL-4)-dependent proliferation of phytohemagglutinin (PHA) activated T cells noncompetitively with respect to cytokine by blocking the IL-4-induced heterodimerization of IL-4Ralpha and gammac receptor chains. Affinities for the binding of IL-4 to Cos-7 cells transfected with huIL-4Ralpha, and to PHA blasts expressing both IL-4Ralpha and gammac, were used to estimate the affinity of the key interaction between gammac and the binary IL-4Ralpha.IL-4 complex on the cell surface. This affinity was defined in terms of the dimensionless ratio [IL-4Ralpha.IL-4.gammac]/[IL-4Ralpha.IL-4], which we designate KR. The results show that on PHA blasts this interaction is relatively weak; KR approximately 9, implying that approximately 10% of the limiting IL-4Ralpha chain remains free of gammac even at saturating concentrations of IL-4. This quantitative treatment establishes KR as a key measure of the coupling between ligand binding and receptor activation, providing a basis for functional distinctions between different receptors that are activated by ligand-induced receptor dimerization.

IL-4 and IL-13 specifically increase adhesion molecule and inflammatory cytokine expression in human lung fibroblasts.

Subepithelial fibrosis in the bronchi of asthmatics is the result of an irreversible lung fibroblast activation, triggered by cytokines secreted by IL-4- and IL-5-activated inflammatory cells. Here, we provide evidence that human lung fibroblasts (ICIG7 cells) express a single class of high-affinity IL-4 receptor (IL-4R). This receptor is functional and composed of at least the IL-4Ralpha and IL-13Ralpha1 chains in the absence of the IL-2Rgamma chain. The IL-4Ralpha is efficiently internalized at 37 degrees C within 15 min in the presence of IL-4, whereas this process is slower with IL-13. In ICIG7 cells, IL-4 triggers the tyrosine phosphorylation of at least two proteins (110 and 180 kDa), and up-regulates the transcription of c-fos, c-jun and c-myc proto-oncogenes. In addition, the secretion of several cytokines [IL-6, granulocyte colony stimulating factor and granulocyte macrophage colony stimulating factor (GM-CSF)] as well as the expression of beta1 integrin and VCAM-1 adhesion molecules are augmented by IL-4. IL-13 displays similar biological activities, but less effectively than IL-4. On the other hand, ICIG7 cells could constitute a lung fibroblast population defined by the spontaneous release of several pro-inflammatory cytokines (IL-6, IL-11 and GM-CSF) and cell surface phenotype (CD4 and Thy-1). Through this peculiar cytokine pattern and the IL-4/IL-13-dependent activities, these cells could act as effector cells in the pathogenesis of asthma, triggering and maintaining the recruitment, homing and activation of bone marrow-derived inflammatory cells, and playing a role in the remodeling process of the airways.

Signaling through interleukin-6 receptor supports blast cell proliferation in acute myeloblastic leukemia.

The role of the interleukin-6/interleukin-6 receptor (IL-6/IL-6R) system in regulating blast cell growth in 8 acute myeloblastic leukemia (AML) patient-derived cell lines was investigated. As they all expressed IL-6R and as none of them responded to exogenous IL-6 under conventional serum-supplemented culture conditions, we investigated whether signaling through IL-6R plays any role in maintaining their spontaneous colony growth. This was done by treating the cells with monoclonal antibodies made against the ligand-specific IL-6R alpha-chain or the signal transducer gp130. In serum-supplemented cultures inhibition of gp130 function did not affect the cell line growth, whereas anti-IL-6R alpha-chain antibody reduced colony growth. While some of the cell lines also showed similar growth characteristics in a serum-free environment, some others changed their growth pattern and stopped responding to anti-IL-6R alpha-chain treatment. At the same time, these cell lines also began to respond to exogenously added IL-6 and, interestingly, were stimulated by anti-gp130 antibody. Hence, in some of the blast cells, clonogenic cell growth seemed to be also negatively controlled by an endogenously produced growth-depressing cytokine or cytokines that utilize gp130. All the cell lines, whether cultured in the presence or absence of serum expressed IL-6 both at mRNA and protein level. The current results indicate that AML cells can use IL-6 as a growth stimulating factor, supplied either paracrinely or autocrinely. This could implicate the use of anti-IL-6R alpha-chain antagonists in AML treatment, not IL-6.

Interleukin (IL) 4 and IL-13 act on human lung fibroblasts. Implication in asthma.

Airway hyperresponsiveness leading to subepithelial fibrosis is mediated by inflammatory cells activated by T helper (Th) 2-derived cytokines such as IL-4 and IL-5. By analyzing the phenotype and response of human lung fibroblasts derived from either fetal (ICIG7) or adult (CCL202) tissue as well as from a Th2-type stromal reaction (FPA) to IL-4 and IL-13, we provide evidence that human lung fibroblasts may behave as inflammatory cells upon activation by IL-4 and IL-13. We show that the three types of fibroblasts constitute different populations that display a distinct pattern in cell surface molecule expression and proinflammatory cytokine and chemokine release. All fibroblasts express functional but different IL-4/IL-13 receptors. Thus, while IL-4 receptor (R) alpha and IL-13Ralpha1 chains are present in all the cells, CCL202 and FPA fibroblasts coexpress the IL-13Ralpha2 and the IL-2Rgamma chain, respectively, suggesting the existence of a heterotrimeric receptor (IL-4Ralpha/IL-13Ralpha/IL-2Rgamma) able to bind IL-4 and IL-13. Stimulation with IL-4 or IL-13 triggers in the fibroblasts a differential signal transduction and upregulation in the expression of beta1 integrin and vascular cell adhesion molecule 1 and in the production of IL-6 and monocyte chemoattractant protein 1, two inflammatory cytokines important in the pathogenesis of allergic inflammation. Our results suggest that when activated by IL-4 and IL-13, different subsets of lung fibroblasts may act as effector cells not only in the pathogenesis of asthma but also in lung remodeling processes. They may also differentially contribute to trigger and maintain the recruitment, homing, and activation of inflammatory cells.

Interleukin-12 Inhibits Graft-Versus-Host Disease Through an Fas-Mediated Mechanism Associated With Alterations in Donor T-Cell Activation and Expansion

AbstractWe have recently made the paradoxical observation that a single injection of recombinant murine interleukin-12 (IL-12) on the day of bone marrow transplantation (BMT) inhibits graft-versus-host disease (GVHD) in lethally irradiated mice receiving fully major histocompatability complex (MHC)-mismatched bone marrow and spleen cells. We have now examined the mechanism of this effect of IL-12 on acute GVHD. By day 4 post-BMT, IL-12–treated mice showed marked reductions in splenic donor CD4+and CD8+T cells compared with GVHD controls. Expression of the early activation markers IL-2R alpha chain (CD25) and CD69 on splenic donor CD4+cells was considerably higher at early time points (36 and 72 hours post-BMT) in IL-12–treated mice compared with GVHD controls. However, the later, GVHD-associated increase in CD25 and very late antigen-4 (VLA-4) expression on donor T cells was greatly depressed in IL-12–protected mice compared with GVHD controls. The marked GVHD-associated expansion of host-reactive T helper cells by day 4 was also completely inhibited in the IL-12–treated group. Expression of Fas was increased on donor CD4 cells of IL-12–treated mice compared with those of controls on days 3 through 7 post-BMT. Furthermore, the ability of IL-12 to protect against GVHD was at least partially dependent on the ability of donor cells to express functional Fas molecules. We conclude that IL-12 treatment at the time of BMT markedly perturbs the activation of alloreactive donor CD4+T cells that play a critical role in the pathogenesis of acute GVHD. We hypothesize that these perturbations culminate in Fas-dependent apoptosis of donor T cells, thus impeding their expansion and their GVHD-promoting activity.

Interleukin-12 Inhibits Graft-Versus-Host Disease Through an Fas-Mediated Mechanism Associated With Alterations in Donor T-Cell Activation and Expansion

We have recently made the paradoxical observation that a single injection of recombinant murine interleukin-12 (IL-12) on the day of bone marrow transplantation (BMT) inhibits graft-versus-host disease (GVHD) in lethally irradiated mice receiving fully major histocompatability complex (MHC)-mismatched bone marrow and spleen cells. We have now examined the mechanism of this effect of IL-12 on acute GVHD. By day 4 post-BMT, IL-12–treated mice showed marked reductions in splenic donor CD4+ and CD8+ T cells compared with GVHD controls. Expression of the early activation markers IL-2R alpha chain (CD25) and CD69 on splenic donor CD4+ cells was considerably higher at early time points (36 and 72 hours post-BMT) in IL-12–treated mice compared with GVHD controls. However, the later, GVHD-associated increase in CD25 and very late antigen-4 (VLA-4) expression on donor T cells was greatly depressed in IL-12–protected mice compared with GVHD controls. The marked GVHD-associated expansion of host-reactive T helper cells by day 4 was also completely inhibited in the IL-12–treated group. Expression of Fas was increased on donor CD4 cells of IL-12–treated mice compared with those of controls on days 3 through 7 post-BMT. Furthermore, the ability of IL-12 to protect against GVHD was at least partially dependent on the ability of donor cells to express functional Fas molecules. We conclude that IL-12 treatment at the time of BMT markedly perturbs the activation of alloreactive donor CD4+ T cells that play a critical role in the pathogenesis of acute GVHD. We hypothesize that these perturbations culminate in Fas-dependent apoptosis of donor T cells, thus impeding their expansion and their GVHD-promoting activity.

Regulatory CD4 T cells: expression of IL-2R alpha chain, resistance to clonal deletion and IL-2 dependency.

We recently characterized a CD4+ T cell population expressing the IL-2R alpha chain (CD25), producing IL-10 and resisting clonal deletion induced by viral superantigen (vSAG) encoded by mouse mammary tumor virus [MMTV(SW)]. We now report that these apoptosis-resistant cells are generated in the thymus but not from the immature CD4+ CD8+ thymocytes. They migrate from the thymus and are found in the periphery from at least the 10th day of life, after which they expand with the same kinetics in normal and MMTV(SW)-infected mice. Their strong capacity for expansion in the periphery makes this population insensitive to thymectomy in adulthood. CD4+ CD25+ cells were totally dependent on exogenous IL-2 for growth in vitro and in vivo, and were missing in IL-2 knockout (KO) mice. The absence of this population and/or an inability to produce IL-10 may be the missing link between IL-2R alpha KO, IL-2 KO and IL-10 KO mice, which all die of inflammatory bowel disease.

Regulation of Interleukin-13 Receptor Constituents on Mature Human B Lymphocytes

Human B cells stimulated through both their immunoglobulin and CD40 receptors up-regulate 745 +/- 51 interleukin (IL)-13 ligand binding sites with an affinity of 0.91 +/- 0.08 nM within 24 h. IL-13 binds primarily to the IL-13Ralpha1 with subsequent sequestration of the IL-4Ralpha into the complex. IL-13Ralpha1 may also be found in those receptors capable of binding IL-4. gamma chain (gammac) participates in receptors capable of binding IL-4 but is not found in association with bound IL-13. Dimeric receptors composed of the IL-4Ralpha complexed with either the IL-13Ralpha1 or gammac occur simultaneously within defined B cell populations. mRNAs for all receptor constituents are increased subsequent to immunoglobulin stimulation alone, while maximal expression of IL-13Ralpha1 is more dependent upon co-stimulation of immunoglobulin and CD40 receptors. mRNA levels for IL-13Ralpha1 vary over a wider range subsequent to surface stimulation than other receptor components. Although gammac is not bound to IL-13 in B cells under the conditions evaluated, it may influence IL-13 binding by competing with IL-13Ralpha1 for association/sequestration with the IL-4Ralpha chain. IL-13Ralpha2 does not participate in the IL-13 receptor that is up-regulated upon activation of quiescent tonsillar B lymphocytes, although mRNA for the protein may be found in the centroblastic fraction of tonsillar cells.

The circulating common gamma chain (CD132) in inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by T cell activation. Activated T cells shed interleukin-2 receptors (IL-2R) in a soluble form. A positive correlation between sIL-2Ralpha (CD25) and disease activity is well documented in IBD, whereas IL-2Rgamma (CD132) has not been investigated in this respect. Sera from 42 patients with ulcerative colitis (UC), 34 with Crohn's disease (CD), 31 healthy volunteers, and 12 patients with infectious enterocolitis were obtained.Disease activity was scored according to a semiquantitative score for UC and CD. sIL-2R alpha chain and gamma chain were assessed by sandwich ELISA techniques using monoclonal antibodies specific for CD25 and CD132, respectively.The concentration of IL-2Ralpha chain (CD25) was found to be median 3.8 ng/ml in healthy volunteers versus 7.0 ng/ml in UC patients (p < 0.001), and 9.6 ng/ml in CD patients (p < 0.001). With respect to IL-2Rgamma (CD132), significantly higher amounts were found in CD patients: 6.6 ng/ml as compared with healthy controls <1.0 ng/ml (p < 0.004). A Kruskal-Wallis test revealed a significant correlation between alpha chain and disease activity in CD (p < 0.001), and further significantly higher gamma chain levels were found in active CD (p = 0.03). For UC patients, a statistically significant increase of the alpha chain with increasing disease activity (p < 0.01) was observed, whereas no significant changes of the gamma chain levels were found (p > 0.05). A difference of gamma chain levels were found between CD and UC in moderate and severe disease activity (p < 0.05). Further analyses revealed that mesalazine did not influence the IL-2Ralpha or -gamma concentration either in UC or in CD patients.An increased circulating level of the soluble common gamma chain (CD132) seems to be found in CD, and an overlap exists between CD and UC.

Interleukin-15 as a potential regulator of the innate immune response.

Interleukin-15 (IL-15) is a newly-discovered cytokine that is produced by activated monocytes early in the course of the innate immune response. IL-15 is able to bind to components of the interleukin-2 receptor (IL-2R) despite the fact that it has no sequence homology with IL-2. IL-15 stimulates human natural killer cell proliferation, cytotoxicity, and cytokine production and can substitute for IL-2 under most conditions. In vitro studies indicate that monocyte-derived IL-15 may be an important determinant of IFN-gamma production by NK cells. In addition, IL-15 is able to promote the survival of natural killer cells under serum-free conditions. The IL-15 receptor is a heterotrimeric complex which is composed of the IL-2R beta and gamma chains in combination with a unique alpha chain (IL-15 alpha). The IL-15R alpha chain has strong sequence homology to the IL-2R alpha chain and confers high affinity binding to the IL-15R. In contrast to IL-2, transcript for IL-15 and IL-15 alpha is expressed in a number of tissues and indicates that IL-15 may be an important ligand for cells that express components of the IL-2R.

Cellular requirements for the activation and proliferation of ruminant gammadelta T cells.

Requirements for the activation and proliferation of gammadelta T cells were investigated. Maximum numbers of gammadelta T cells expressed the IL-2R alpha-chain after 6-h Con A stimulation in peripheral blood, efferent lymph, and afferent lymph. In comparison, IL-2R alpha-chain expression on CD4 T cells only reached maximum levels in response to Con A stimulation in peripheral blood and afferent lymph populations. Analysis of enriched gammadelta T cells demonstrated that Con A-induced expression of the IL-2R alpha-chain was independent of APC. Together, these data suggest that the requirements for gammadelta T cell activation are less stringent than those for alphabeta T cell activation. Unfractionated peripheral blood, efferent lymph, and afferent lymph cell populations proliferated in response to Con A alone. In contrast, enriched gammadelta T cells (CD4/CD8 depleted) from efferent lymph did not proliferate in response to Con A alone, but required the addition of IL-2. This requirement for exogenous IL-2 could be overcome by the addition of dendritic cells purified from afferent lymph. These results suggested that gammadelta T cells required costimulatory signals provided by APC to ensure the production of sufficient IL-2 to drive proliferation. CD28 and CTLA-4 mRNA were detected in efferent lymph and afferent lymph populations containing CD4 and CD8 T cells stimulated with Con A and IL-2 or with Con A alone, respectively. In contrast, negligible levels of these mRNA species were detected in efferent and afferent lymph populations devoid of CD4 and CD8 T cells. These results suggest that ovine gammadelta T cells may use alternative costimulatory pathways.

Receptor-associated constitutive protein tyrosine phosphatase activity controls the kinase function of JAK1.

Exposure of cells to protein tyrosine phosphatase (PTP) inhibitors causes an increase in the phosphotyrosine content of many cellular proteins. However, the level at which the primary signaling event is affected is still unclear. We show that Jaks are activated by tyrosine phosphorylation in cells that are briefly exposed to the PTP inhibitor pervanadate (PV), resulting in tyrosine phosphorylation and functional activation of Stat6 (in addition to other Stats). Mutant cell lines that lack Jak1 activity fail to support PV-mediated [or interleukin 4 (IL-4)-dependent] activation of Stat6 but can be rescued by complementation with functional Jak1. The docking sites for both Jak1 and Stat6 reside in the cytoplasmic domain of the IL-4 receptor alpha-chain (IL-4Ralpha). The glioblastoma-derived cell lines T98G, GRE, and M007, which do not express the IL-4Ralpha chain, fail to support Stat6 activation in response to either IL-4 or PV. Complementation of T98G cells with the IL-4Ralpha restores both PV-mediated and IL-4-dependent Stat6 activation. Murine L929 cells, which do not express the gamma common chain of the IL-4 receptor, support PV-mediated but not IL-4-dependent Stat6 activation. Thus, Stat6 activation by PV is an IL-4Ralpha-mediated, Jak1-dependent event that is independent of receptor dimerization. We propose that receptor-associated constitutive PTP activity functions to down-regulate persistent, receptor-linked kinase activity. Inhibition or deletion of PTP activity results in constitutive activation of cytokine signaling pathways.

A Kaposi's Sarcoma-associated Herpesvirus-encoded Cytokine Homolog (vIL-6) Activates Signaling through the Shared gp130 Receptor Subunit

The present studies analyzed the biologic activity of a gene product (vIL-6) encoded by the recently discovered Kaposi's sarcoma-associated herpesvirus (KSHV) bearing 24.8% amino acid identity with human interleukin-6 (huIL-6). Based on this similarity, we hypothesized that this viral homolog might trigger the JAK/STAT pathway, which typically is engaged by IL-6 and other cytokines. Activation of receptor-associated Janus tyrosine kinases (JAKs) results in the subsequent phosphorylation of signal transducers and activators of transcription (STATs) leading to nuclear entry and transcriptional regulation of target genes. Treatment of HepG2 cells with culture medium containing recombinant KSHV-encoded vIL-6 led to rapid induction of JAK1 phosphorylation and a nuclear DNA-binding activity found to contain STAT1 and STAT3. An antibody to the IL-6 receptor (IL-6R) alpha subunit effectively neutralized the response to huIL-6 but failed to block STAT activation by vIL-6. In contrast, an antibody reactive with the gp130 subunit of IL-6R abrogated signaling of both responses. Moreover, a transfected cell line expressing human gp130 without IL-6Ralpha exhibited a robust response to vIL-6 but not to huIL-6. These results demonstrate that KSHV encodes a cytokine that activates specific JAK/STAT signaling via interactions with the gp130 signal transducing subunit independently of the IL-6Ralpha chain. This activity may have an impact on gp130-mediated signaling in response to native cytokines and thereby influence disease pathogenesis upon KSHV infection.

The IL-4 receptor alpha-chain cytoplasmic domain is sufficient for activation of JAK-1 and STAT6 and the induction of IL-4-specific gene expression.

The common gamma-chain (gamma(c)) is a functional component of the IL-4R, yet cells lacking gamma(c) are able to respond to IL-4. This has led to the suggestion that a surrogate gamma'-chain, which can interact with the IL-4R alpha chain to mediate signaling, is expressed on cells lacking gamma(c). An alternative possibility is that in the absence of gamma(c), the IL-4R alpha chain is able to transduce signals by homodimerization. To test this latter possibility, a chimeric receptor containing the extracellular domain of c-kit (the stem cell factor (SCF) receptor) and the cytoplasmic and transmembrane domains of the IL-4R alpha chain was generated. Treatment of cells expressing the chimeric receptor kit/IL-4R alpha with SCF induces activation of the IL-4R alpha-associated kinase JAK-1 and the transcription factor STAT6. However, tyrosine phosphorylation of JAK-3, which associates with gamma(c), is not induced by SCF in these cells. SCF-mediated ligation of kit/IL-4R alpha is sufficient to elicit IL-4-specific gene expression, including up-regulation of CD23 and synthesis of germ-line epsilon transcripts. In the T cell line CTLL2, ligation of kit/IL-4R alpha induces cellular proliferation. Finally, in JAK-1-deficient HeLa cells, STAT6 activation by IL-4 is completely abolished. Together, these data demonstrate that the IL-4R alpha cytoplasmic domain is sufficient to activate JAK-1 and STAT6 and to induce expression of IL-4 target genes, thus identifying a mechanism by which IL-4 signaling can proceed in the absence of JAK-3 and gamma(c).

Pattern of cytokine receptors expressed by human dendritic cells migrated from dermal explants.

Different reasons account for the lack of information about the expression of cytokine receptors on human dendritic cells (DC): (a) DC are a trace population; (b) the proteolytic treatment used to isolate DC may alter enzyme-sensitive epitopes; and (c) low numbers of receptors per cell. In the present work the expression of cytokine receptors was analysed by flow cytometry on the population of dermal DC (DDC) that spontaneously migrate from short-term culture dermal explants. DDC obtained after dermal culture were CD1alow, CD1b+, CD1c+, human leucocyte antigen (HLA)-DR+, CD11chigh, CD11b+ and CD32+. The DC lineage was confirmed by ultrastructural analysis. DDC expressed interleukin (IL)-1R type 1 (monoclonal antibody (mAb) hIL-1R1-M1; and 6B5); IL-1R type 2 (mAb hIL-1R2-M22); IL-2R alpha chain (mAb anti-Tac; and hIL-2R-M1) and IL-2R gamma chain (mAb 3B5; and AG14C). DDC did not stain for IL-2R beta chain using four mAbs recognizing two different epitopes of IL-2R beta (mAb 2R-B; Mik-beta 1; and CF1; Mik-beta 3, respectively). DDC were also positive for the cytokine binding chains (alpha chains) of IL-3R (mAb 9F5); IL-4R (mAb hIL-4R-M57; and S456C9); and IL-7R (mAb hIL-7R-M20; and R3434). DDC showed low levels of IL-6R alpha chain (mAb B-F19; B-R6; and B-E23) and its signal transducer gp130 (mAb A2; and B1). DDC strongly expressed interferon-gamma receptor (IFN-gamma R) (mAb GIR-208) and were negative for IL-8R (mAb B-G20; and B-F25). All DDC were highly positive for granulocyte-macrophage colony-stimulating factor receptor (GM-CSFR) alpha chain (mAb hGM-CSFR-M1; SC06; SC04, and 8G6) and to a lesser extent for the common beta chain of GM-CSFR, IL-3R and IL-5R (mAb 3D7). On the other hand, reactivity was not found for granulocyte colony-stimulating factor receptor (G-CSFR) (mAb hGCSFR-M1) nor macrophage colony-stimulating factor receptor (M-CSFR) (mAb 7-7A3-17) confirming the DC lineage of DDC. As previously reported for lymphoid DC, DDC expressed tumour necrosis factor receptort (TNFR) 75000 MW (mAb utr-1; hTNFR-M1; and MR2-1) but lacked TNFR 55000 MW (mAb htr-9; MR1-1; and MR1-2). In summary, DDC express receptors for a broad panel of cytokines, even receptors for cytokines whose effects on DC are still unknown (i.e. IL-2R alpha gamma; IL-6R alpha/gp 130; IL-7R alpha gamma).

Altered interleukin-2 receptor alpha-chain is expressed in human T-cell leukaemia virus type-I-infected T-cell lines and human peripheral blood mononuclear cells of adult T-cell leukaemia patients through an alternative splicing mechanism.

A polymerase chain reaction (PCR) method was used to detect the interleukin-2 receptor alpha-chain (IL-2R alpha) chain which lacks the conventional transmembrane (TM) domain in mRNA from human T-cell leukaemia virus type-I (HTLV-I)-infected cell lines or peripheral blood mononuclear cells (PBMC) isolated from adult T-cell leukaemia (ATL) patients. Primer pairs encompassing the TM domain were selected to generate a 357-base pair (bp) fragment. A 146-bp PCR product was observed consistently in addition to the target 357-bp PCR product in mRNA from HTLV-I-infected cell lines, such as MT-1, MT-2, MT-4 and in PBMC isolated from ATL patients. However, this 146-bp PCR product was undetectable in HTLV-I-negative cell lines. The product was also detected in PBMC from normal individuals if activated in vitro with phytohaemagglutinin but not without stimulation. DNA sequence analyses revealed that exons from 5 to 7, which define a 211-bp region containing the conventional TM domain, were deleted in the 146-bp PCR product. The C-terminal amino acid sequence starting from Gly174 of the 211-bp-deleted molecule was distinct from that of conventional IL-2R alpha as a result of an altered reading frame. We identified a 45000 MW peptide generated from IL-2R alpha mRNA through this exon skip in cell lysate of MT-1 and MT-2 by Western blot analyses using an antibody raised against the peptides specific to an altered IL-2R alpha. Our results indicate that an altered IL-2R alpha chain is expressed in HTLV-I-infected T lymphocytic cell lines and in ATL patients.

Interleukin-15 signals T84 colonic epithelial cells in the absence of the interleukin-2 receptor beta-chain.

Interleukin-15 (IL-15) shares many biological functions with interleukin-2 (IL-2) due to common receptor components. IL-15 binds to the IL-2 receptor (IL-2R) beta-chain and the common gamma-chain receptor in addition to one other IL-15 binding receptor protein (IL-15R alpha). Both IL-2R beta- and gamma-chains are required to promote cell growth in hematopoietic cells. The colonic cryptlike epithelial cell line T84 contains the common gamma-chain but lacks the IL-2R beta-chain. We report IL-15R alpha-chain mRNA in T84 cells with the use of reverse transcriptase-polymerase chain reaction. T84 and normal colonic epithelial cells bind a FLAG-IL-15 fusion protein in immunoperoxidase and flow cytometric experiments. In addition, IL-15, but not IL-2, accelerates and enhances the development of transepithelial resistance across T84 monolayers in a dose-dependent fashion. We conclude that normal and T84 colonic epithelial cells express IL-15R alpha and are able to bind IL-15. IL-15 can deliver a nonproliferative functional signal in the absence of IL-2R beta-chain in T84 cells.

A novel 4-kb interleukin-13 receptor alpha mRNA expressed in human B, T, and endothelial cells encoding an alternate type-II interleukin-4/interleukin-13 receptor.

A 4 kb human interleukin-13 receptor (IL-13R) chain cDNA was cloned from a B cell cDNA library using expressed sequence tags homologous to mouse IL-13R as probes. The deduced protein sequence shows a significant level of sequence identity with the IL-5R and the human IL-13R identified recently by expression cloning. The cytoplasmic region is very highly conserved between human and mouse homologs and contains a consensus binding motif for a signal transducer and activator of transcription. The cDNA encodes a protein binding IL-13 when expressed alone which participates in a receptor complex for both IL-4 and IL-13 when expressed in conjunction with the IL-4R alpha chain. Transcripts for this IL-13R chain could be detected in most tissues and organs studied and in T, B, endothelial cells, basophilic, immature mast cell, and monocytic cell lines. The pattern of expression is different from the other recently cloned IL-13R molecule, and correlates with sites where IL-4 and IL-13 signaling is known to occur. This novel receptor is therefore likely to be implicated in reactions involved in IgE responses, T helper 2 differentiation, adhesion of leukocytes to endothelium, and therefore in pathological phenomena such as allergy, atopy, and asthma.