Mediation of interleukin-11-dependent biological responses by a soluble form of the interleukin-11 receptor

The interleukin-11 receptor variant p.W307R results in craniosynostosis in humans

Craniosynostosis is characterized by the premature fusion and ossification of one or more of the sutures of the calvaria, often resulting in abnormal features of the face and the skull. In cases in which growth of the brain supersedes available space within the skull, developmental delay or cognitive impairment can occur. A complex interplay of different cell types and multiple signaling pathways are required for correct craniofacial development. In this study, we report on two siblings with craniosynostosis and a homozygous missense pathogenic variant within the IL11RA gene (c.919 T > C; p.W307R). The patients present with craniosynostosis, exophthalmos, delayed tooth eruption, mild platybasia, and a basilar invagination. The p.W307R variant is located within the arginine-tryptophan-zipper within the D3 domain of the IL-11R, a structural element known to be important for the stability of the cytokine receptor. Expression of IL-11R-W307R in cells shows impaired maturation of the IL-11R, no transport to the cell surface and intracellular retention. Accordingly, cells stably expressing IL-11R-W307R do not respond when stimulated with IL-11, arguing for a loss-of-function mutation. In summary, the IL-11R-W307R variant, reported here for the first time to our knowledge, is most likely the causative variant underlying craniosynostosis in these patients.

Interleukin-11 receptor subunit α-1 is required for maximal airway responsiveness to methacholine after acute exposure to ozone

Interleukin (IL)-11, a multifunctional cytokine, contributes to numerous biological processes, including adipogenesis, hematopoiesis, and inflammation. Asthma, a respiratory disease, is notably characterized by reversible airway obstruction, persistent lung inflammation, and airway hyperresponsiveness (AHR). Nasal insufflation of IL-11 causes AHR in wild-type mice while lung inflammation induced by antigen sensitization and challenge, which mimics features of atopic asthma in humans, is attenuated in mice genetically deficient in IL-11 receptor subunit α-1 (IL-11Rα1-deficient mice), a transmembrane receptor that is required conjointly with glycoprotein 130 to transduce IL-11 signaling. Nevertheless, the contribution of IL-11Rα1 to characteristics of nonatopic asthma is unknown. Thus, based on the aforementioned observations, we hypothesized that genetic deficiency of IL-11Rα1 attenuates lung inflammation and increases airway responsiveness after acute inhalation exposure to ozone (O3), a criteria pollutant and nonatopic asthma stimulus. Accordingly, 4 and/or 24 h after cessation of exposure to filtered room air or O3, we assessed lung inflammation and airway responsiveness in wild-type and IL-11Rα1-deficient mice. With the exception of bronchoalveolar lavage macrophages and adiponectin, which were significantly increased and decreased, respectively, in O3-exposed IL-11Rα1-deficient as compared with O3-exposed wild-type mice, no other genotype-related differences in lung inflammation indices that we quantified were observed in O3-exposed mice. However, airway responsiveness to acetyl-β-methylcholine chloride (methacholine) was significantly diminished in IL-11Rα1-deficient as compared with wild-type mice after O3 exposure. In conclusion, these results demonstrate that IL-11Rα1 minimally contributes to lung inflammation but is required for maximal airway responsiveness to methacholine in a mouse model of nonatopic asthma.

Xenopus laevis il11ra.L is an experimentally proven interleukin-11 receptor component that is required for tadpole tail regeneration

Xenopus laevis tadpoles possess high regenerative ability and can regenerate functional tails after amputation. An early event in regeneration is the induction of undifferentiated cells that form the regenerated tail. We previously reported that interleukin-11 (il11) is upregulated immediately after tail amputation to induce undifferentiated cells of different cell lineages, indicating a key role of il11 in initiating tail regeneration. As Il11 is a secretory factor, Il11 receptor-expressing cells are thought to mediate its function. X. laevis has a gene annotated as interleukin 11 receptor subunit alpha on chromosome 1L (il11ra.L), a putative subunit of the Il11 receptor complex, but its function has not been investigated. Here, we show that nuclear localization of phosphorylated Stat3 induced by Il11 is abolished in il11ra.L knocked-out culture cells, strongly suggesting that il11ra.L encodes an Il11 receptor component. Moreover, knockdown of il11ra.L impaired tadpole tail regeneration, suggesting its indispensable role in tail regeneration. We also provide a model showing that Il11 functions via il11ra.L-expressing cells in a non-cell autonomous manner. These results highlight the importance of il11ra.L-expressing cells in tail regeneration.

The cytokine interleukin-11 crucially links bone formation, remodeling and resorption

Bone development is a complex process that requires the activity of several different signaling pathways and cell types. It involves the coordinated action of osteoclasts (cells that are capable of resorbing bone), osteoblasts (cells that are able to form bone), osteocytes (cells that form a syncytial network within the bone), skeletal muscle cells and the bone marrow. In recent years, the cytokine interleukin-11 (IL-11), a member of the IL-6 family of cytokines, has emerged as an important regulatory protein for bone formation, remodeling and resorption. Furthermore, coding missense mutations in the IL11RA gene, which encodes the IL-11 receptor (IL-11R), have recently been linked to craniosynostosis, a human disease in which the sutures that line the head bones close prematurely. This review summarizes current knowledge about IL-11 and highlights its role in bone development and homeostasis. It further discusses the specificity and redundancy provided by the other members of the IL-6 cytokine family and how they facilitate signaling and cross-talk between skeletal muscle cells, bone cells and the bone marrow. We describe their actions in physiological and in pathological states and discuss how this knowledge could be translated into therapy.

Pharmacokinetic and Pharmacodynamic Evaluation of Different PEGylated Human Interleukin-11 Preparations in Animal Models

Treating thrombocytopenia induced by chemotherapy remains an unmet-medical need. The use of recombinant human interleukin-11 (rhIL-11) requires repeated injections and induces significant fluid retention in some patients. Modification of human interleukin-11 with chemically inert polyethylene glycol polymer (PEG) may extend the peripheral circulation half-life leading to an improved pharmacokinetic and pharmadynamic profile. In this study, a number of rhIL-11 PEG conjugates were created to determine the optimal approach to prolong circulating half-life with the most robust pharmacological effect. The lead candidate was found to be a single 40-kDa Y-shaped PEG linked to the N-terminus, which produced a long-lasting circulating half-life, enhanced efficacy and alleviated side effect of dilutional anemia in healthy rat models. This candidate was also shown to be effective in myelosuppressive rats in preventing the occurrence of severe thrombocytopenia while ameliorating dilutional anemia, compared to rats receiving daily administration of unmodified rhIL-11 at the same dose. These data indicated that a single injection of the selected modified rhIL-11 for each cycle of chemotherapy regimen is potentially feasible. This approach may also be useful in treating patients of acute radiation syndrome when frequent administration is not feasible in a widespread event of a major radiation exposure.

Efficient expression and isolation of recombinant human interleukin-11 (rhIL-11) in Pichia pastoris

Current source of recombinant human interleukin-11 (rhIL-11) is isolated from a fusion protein expressed by E. coli that requires additional enterokinase to remove linked protein, resulting in product heterogeneity of N-terminal sequence. Due to lack of glycosylation, rhIL-11 is suitable to be expressed by yeast cells. However, the only available yeast-derived rhIL-11 presents an obstacle in low production yield, as well as an unamiable process, such as the use of reverse-phase chromatography employing plenty of toxic organic solvents. Our findings showed that the low yield was due to self-aggregation of rhIL-11. A novel process recovering bioactive rhIL-11 from the yeast secretory medium therefore has been developed and demonstrated, involving fermentation from Pichia pastoris, followed by a two-phase extraction to precipitate rhIL-11. After renaturing, the protein of interest was purified by a two-column step, comprising a cation-exchanger, and a hydrophobic interaction chromatography in tandem at high sample loads that was facile and cost-effective in future scale-up. Identity and quality assessments confirmed the expected amino acid sequence without N-terminal heterogeneity, as well as high quality in potency and purity. Such a process provides an alternative and adequate supply of the starting material for the PEGylated rhIL-11.

Preclinical evaluation of the mono-PEGylated recombinant human interleukin-11 in cynomolgus monkeys

The mono-PEGylated recombinant human interleukin-11 (rhIL-11) was evaluated for its pharmacology and toxicology profile in non-human primates. This PEGylated IL-11 (PEG-IL11) showed a much prolonged circulating half-life of 67h in cynomolgus monkeys as compared to its un-PEGylated counterpart (~3h) through subcutaneous administration, implicating that a single injection of the recommended dose will effectively enhance thrombopoiesis in humans for a much longer period of time compared to rhIL-11 in humans (t_1/2=6.9h). The toxicokinetics study of single dose and multiple doses showed that systemic exposure was positively correlated with the dosing level, implying that efficacy and toxicity were mechanism-based. A single high dose at 6.25mg/kg through subcutaneous route revealed tolerable and transient toxicity. Multiple-dose in monkeys receiving 0.3mg/kg weekly of the drug developed only mild to moderate toxicity. Major adverse events and immunogenicity in monkeys were only observed in the overdose groups. Bones were positively impacted; while reversible toxicities in heart, liver, kidney and lung observed were likely to be consequences of fluid retention. In summary, the PEG moiety on rhIL-11 did not elicit additional toxicities, and the drug under investigation was found to be well tolerated in monkeys after receiving a single effective dose of 0.1-0.3mg/kg through subcutaneous delivery, which may be allometrically scaled to a future clinical dose at 30-100μg/kg, creating a potential long acting, safer, and more convenient treatment approach based on rhIL-11.

interleukin-11 induces and maintains progenitors of different cell lineages during Xenopus tadpole tail regeneration

Unlike mammals, Xenopus laevis tadpoles possess high ability to regenerate their lost organs. In amphibians, the main source of regenerated tissues is lineage-restricted tissue stem cells, but the mechanisms underlying induction, maintenance and differentiation of these stem/progenitor cells in the regenerating organs are poorly understood. We previously reported that interleukin-11 (il-11) is highly expressed in the proliferating cells of regenerating Xenopus tadpole tails. Here, we show that il-11 knockdown (KD) shortens the regenerated tail length, and the phenotype is rescued by forced-il-11-expression in the KD tadpoles. Moreover, marker genes for undifferentiated notochord, muscle, and sensory neurons are downregulated in the KD tadpoles, and the forced-il-11-expression in intact tadpole tails induces expression of these marker genes. Our findings demonstrate that il-11 is necessary for organ regeneration, and suggest that IL-11 plays a key role in the induction and maintenance of undifferentiated progenitors across cell lineages during Xenopus tail regeneration. Xenopus laevis tadpoles have maintained their ability to regenerate various organs. Here, the authors show that interleukin-11 is necessary for organ regeneration, by inducing and maintaining undifferentiated progenitors across cell lineages during Xenopus tail regeneration.

Generation of Soluble Interleukin-11 and Interleukin-6 Receptors: A Crucial Function for Proteases during Inflammation

The cytokines interleukin-11 (IL-11) and IL-6 are important proteins with well-defined pro- and anti-inflammatory functions. They activate intracellular signaling cascades through a homodimer of the ubiquitously expressed signal-transducing β-receptor glycoprotein 130 (gp130). Specificity is gained through the cell- and tissue-specific expression of the nonsignaling IL-11 and IL-6 α-receptors (IL-11R and IL-6R), which determine the responsiveness of the cell to these two cytokines. IL-6 is a rare example, where its soluble receptor (sIL-6R) has agonistic properties, so that the IL-6/sIL-6R complex is able to activate cells that are usually not responsive to IL-6 alone (trans-signaling). Recent evidence suggests that IL-11 can signal via a similar trans-signaling mechanism. In this review, we highlight similarities and differences in the functions of IL-11 and IL-6. We summarize current knowledge about the generation of the sIL-6R and sIL-11R by different proteases and discuss possible roles during inflammatory processes. Finally, we focus on the selective and/or combined inhibition of IL-6 and IL-11 signaling and how this might translate into the clinics.

A designer hyper interleukin 11 (H11) is a biologically active cytokine

Background

Interleukin 11 (IL-11) is a pleiotropic cytokine with anti-apoptotic, anti-inflammatory and hematopoietic potential. The IL-11 activity is determined by the expression of the IL-11R receptor alpha (IL-11Rα) and the signal transducing subunit β (gp130) on the cell membrane. A recombinant soluble form of the IL-11Rα (sIL-11Rα) in combination with IL-11 acts as an agonist on cells expressing the gp130 molecule. We constructed a designer cytokine Hyper IL-11 (H11), which is exclusively composed of naturally existing components. It contains the full length sIL-11Rα connected with the mature IL-11 protein using their natural sequences only. Such a construct has two major advantages: (i) its components are as close as possible to the natural forms of both proteins and (ii) it lacks an artificial linker what should avoid induction of antibody production.

Results

The H11 construct was generated, the protein was produced in a baculovirus expression system and was then purified by using ion exchange chromatography. The H11 protein displayed activity in three independent bioassays, (i) it induced acute phase proteins production in HepG2 cells expressing IL-11, IL-11Rα and gp130, (ii) it stimulated the proliferation of B9 cells (cells expressing IL-11Rα and gp130) and (iii) proliferation of Baf/3-gp130 cells (cells not expressing IL-11 and IL-11Rα but gp130). Moreover, the preliminary data indicated that H11 was functionally distinct from Hyper-IL-6, a molecule which utilizes the same homodimer of signal transducing receptor (gp130).

Conclusions

The biologically active H11 may be potentially useful for treatment of thrombocytopenia, infertility, multiple sclerosis, cardiovascular diseases or inflammatory disorders.

Birth control vaccine targeting leukemia inhibitory factor

The population explosion and unintended pregnancies resulting in elective abortions continue to impose major public health issues. This calls for a better method of contraception. Immunocontraception has been proposed as a valuable alternative that can fulfill most, if not all, of the properties of an ideal contraceptive. There are several targets that are being explored for contraceptive vaccine development. Leukemia inhibitory factor (LIF), a member of interleukin-6 family, is required for embryo development and successful blastocyst implantation in several mammalian species. The present study was conducted to examine if LIF can be a target for the development of a birth control vaccine. Three sequences from LIF and two sequences from LIF-receptor (LIF-R) that span the regions involved in ligand-receptor binding were delineated, and peptides were synthesized based upon these sequences. Antibodies raised against these five peptides reduced LIF bioactivity in an in vitro culture assay using BA/F3 mLIF-R-mpg130 cells. Vaccines were prepared by conjugating these peptides to various carrier proteins. Immunization of female mice with these peptide vaccines induced a long-lasting, circulating as well as local antibody response in various parts of the genital tract, and resulted in a significant (P ≤ 0.05) inhibition in fertility in all the three trials; the LIF-R peptide vaccines proved to be a better vaccine target. The data indicate that LIF/LIF-R is an excellent target for the development of a birth control vaccine. This is the first study, to our knowledge, that examined LIF/LIF-R as a target for immunocontraception. The findings of this study can be easily translated to humans since LIF/LIF-R is also important for implantation and pregnancy in women.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

Non-core region modulates interleukin-11 signaling activity: generation of agonist and antagonist variants

Human interleukin-11 (hIL-11) is a pleiotropic cytokine administered to patients with low platelet counts. From a structural point of view hIL-11 belongs to the long-helix cytokine superfamily, which is characterized by a conserved core motif consisting of four α-helices. We have investigated the region of hIL-11 that does not belong to the α-helical bundle motif, and that for the purpose of brevity we have termed "non-core region." The primary sequence of the interleukin was altered at various locations within the non-core region by introducing glycosylation sites. Functional consequences of these modifications were examined in cell-based as well as biophysical assays. Overall, the data indicated that the non-core region modulates the function of hIL-11 in two ways. First, the majority of muteins displayed enhanced cell-stimulatory properties (superagonist behavior) in a glycosylation-dependent manner, suggesting that the non-core region is biologically designed to limit the full potential of hIL-11. Second, specific modification of a predicted mini α-helix led to cytokine inactivation, demonstrating that this putative structural element belongs to site III engaging a second copy of cell-receptor gp130. These findings have unveiled new and unexpected elements modulating the biological activity of hIL-11, which may be exploited to develop more versatile medications based on this important cytokine.

Cytokine signalling via gp130 in gastric cancer

Cytokine signalling pathways that depend on gp130 are dysregulated in several epithelial cancers including gastric cancer. It has been established that blockade of SHP2 activation of MAPK signalling results in hyperactivation of STAT3 resulting in increased cell proliferation, angiogenesis, inflammation and inhibition of both immunocyte and epithelial cell apoptosis. Additionally, key genes regulated downstream of gp130 via MAPK activation such as the stomach-specific tumor suppressor gene tff1 are suppressed, contributing to the oncogenic outcome. The main cytokine driver of gp130 signalling in the stomach is IL-11, with IL-6 having little activity in the antral stomach in which most pathology initiates. IL-11 is up-regulated in both mouse and human gastric cancer and in pre-neoplastic mucosa. A characteristic gene signature specifically associated with IL-11 drive has been observed, although the prognostic value of the signature has not yet been assessed. Infection of human or mouse stomach with Helicobacter pylori, especially that expressing the CagA cytotoxin, produces constitutive MAPK activation, but also activated STAT3 and increases IL-11 expression. The possibility of designing and utilising small molecule inhibitors of either IL-11 or STAT3 activation may be worthwhile in developing new cancer therapeutics.

Soluble interleukin-15 receptor alpha (IL-15R alpha)-sushi as a selective and potent agonist of IL-15 action through IL-15R beta/gamma. Hyperagonist IL-15 x IL-15R alpha fusion proteins

Interleukin-15 (IL-15) is crucial for the generation of multiple lymphocyte subsets (natural killer (NK), NK-T cells, and memory CD8 T cells), and transpresentation of IL-15 by monocytes and dendritic cells has been suggested to be the dominant activating process of these lymphocytes. We have previously shown that a natural soluble form of IL-15R alpha chain corresponding to the entire extracellular domain of IL-15R alpha behaves as a high affinity IL-15 antagonist. In sharp contrast with this finding, we demonstrate in this report that a recombinant, soluble sushi domain of IL-15R alpha, which bears most of the binding affinity for IL-15, behaves as a potent IL-15 agonist by enhancing its binding and biological effects (proliferation and protection from apoptosis) through the IL-15R beta/gamma heterodimer, whereas it does not affect IL-15 binding and function of the tripartite IL-15R alpha/beta/gamma membrane receptor. Our results suggest that, if naturally produced, such soluble sushi domains might be involved in the IL-15 transpresentation mechanism. Fusion proteins (RLI and ILR), in which IL-15 and IL-15R alpha-sushi are attached by a flexible linker, are even more potent than the combination of IL-15 plus sIL-15R alpha-sushi. After binding to IL-15R beta/gamma, RLI is internalized and induces a biological response very similar to the IL-15 high affinity response. Such hyper-IL-15 fusion proteins appear to constitute potent adjuvants for the expansion of lymphocyte subsets.

Cytokines, chemokines and growth factors in endometrium related to implantation

The complexity of the events of embryo implantation and placentation is exemplified by the number and range of cytokines with demonstrated roles in these processes. Disturbance of the normal expression or action of these cytokines results in complete or partial failure of implantation and abnormal placental formation in mice or humans. Of known importance are members of the gp130 family such as interleukin-11 (IL-11) and leukaemia inhibitory factor (LIF), the transforming growth factor beta (TGFbeta) superfamily including the activins, the colony-stimulating factors (CSF), the IL-1 system and IL-15 system. New data are also emerging for roles for a number of chemokines (chemoattractive cytokines) both in recruiting specific cohorts of leukocytes to implantation sites and in trophoblast differentiation and trafficking. This review focuses on those cytokines and chemokines whose expression pattern in the human endometrium is consistent with a potential role in implantation and placentation and for which some relevant actions are known. It examines what is known of their regulation and action along with alterations in clinically relevant situations.

Interleukin-11 signaling is required for the differentiation of natural killer cells at the maternal-fetal interface

Interleukin-11 (IL-11) is a multifunctional hematopoietic growth factor that has been implicated in the control of reproduction. Studies on IL-11 receptor-alpha (IL-11R alpha)-deficient mice showed that female mice are infertile due to defective decidualization. In this report, we evaluated the development of decidual cells, immune cells, and the vasculature associated with the implantation site of IL-11R alpha-deficient mice; with the aim of better understanding the nature of the fertility defect. Messenger RNAs for decidual differentiation, such as decidual prolactin-related protein and prolactin-like protein-J are expressed in the IL-11R alpha mutant. However, the number of decidual cells expressing these genes is decreased in the mutant compared with the wild-type control. Although, trophoblast cells differentiate and express placental lactogen-I in the IL-11R alpha-deficient uterine environment, they fail to progress and expand in number. Defects in the organization of the decidual vasculature were also apparent in the IL-11R alpha mutant uterus. The most dramatic effect of IL-11 signaling was on the hematopoietic environment of the uterine decidua. Differentiated/perforin-expressing uterine natural killer (NK) cells were virtually absent from implantation sites of IL-11R alpha mutant mice. NK cell precursors were capable of homing to the IL-11R alpha-deficient uterus and a known regulator of NK cell differentiation; IL-15 was expressed in the IL-11R alpha mutant uterus. Splenic NK cells from IL-11R alpha mutant mice were also able to respond to IL-15 in vitro. Thus, the defect in NK precursor cell maturation was not intrinsic to the NK precursor cells but was dependent upon the tissue environment. In summary, IL-11 signaling is required for decidual-specific maturation of NK cells.

Functional characterization of W147A: a high-affinity interleukin-11 antagonist

IL-11 is a member of the gp130 family of cytokines, which signal via assembly of multisubunit receptor complexes containing at least one molecule of the transmembrane signaling receptor gp130. IL-11 forms a high-affinity complex, thereby inducing gp130-dependent signaling. Previous studies have identified three distinct receptor binding sites, I, II, and III, crucial for the binding of murine IL-11 (mIL-11) to both the IL-11R and gp130. In this study, we have further characterized the role of the mIL-11 site III mutant W147A. We show that W147A is a high-affinity specific antagonist of mIL-11-mediated signaling in gp130/IL-11R-transfected Ba/F3 cells. The antagonistic action of W147A is due to its ability to competitively disrupt multimeric gp130/IL-11R signaling complex formation. We also show that W147A inhibits IL-11-mediated signaling in primary human endometrial cells, thus demonstrating the potential utility of W147A in suppressing IL-11 responses in vivo.

Functionally active fusion protein of the novel composite cytokine CLC/soluble CNTF receptor

The heterodimeric cytokine composed of the soluble ciliary neurotrophic factor receptor (sCNTFR) and the IL-6 family member cardiotrophin-like cytokine (CLC) was recently identified as a new ligand for gp130-leukemia inhibitory factor receptor (LIFR) complex [Plun-Favreau, H., Elson, G., Chabbert, M., Froger, J., deLapeyriere, O., Lelievre, E., Guillet, C., Hermann, J., Gauchat, J. F., Gascan, H. & Chevalier, S. (2001) EMBO J. 20, 1692-1703]. This heterodimer shows overlapping biological properties with LIF. Although CLC contains a putative signal peptide and therefore should enter into the classical secretory pathway, the protein has been shown to be retained within transfected mammalian cells, unless coexpressed with either sCNTFR or cytokine like factor (CLF) [Elson, G. C., Lelievre, E., Guillet, C., Chevalier, S., Plun-Favreau, H., Froger, J., Suard, I., de Coignac, A. B., Delneste, Y., Bonnefoy, J. Y., Gauchat, J. F. & Gascan, H. (2000) Nat. Neurosci. 3, 867-872]. In the present study, we demonstrate that a fusion protein comprising CLC covalently coupled through a glycine/serine linker to sCNTFR (CC-FP) is efficiently secreted from transfected mammalian cells. CC-FP shows enhanced activities in respect to the CLC/sCNTFR native complex, on a number of cells expressing gp130 and LIFR on their surface. In addition, CC-FP is able to compete with CNTF for cell binding, indicating that both cytokines share binding epitope(s) expressed by their receptor complex. Analysis of the downstream signaling events revealed the recruitment by CC-FP of the signal transducer and activator of transcription (STAT)-3, Akt and mitogen-activated protein (MAP) kinase pathways. The monomeric bioactive CLC/sCNTFR fusion protein is therefore a powerful tool to study the biological role of the recently described cytokine CLC.

Engineering and use of (32)P-labeled human recombinant interleukin-11 for receptor binding studies

Human interleukin-11 (hIL-11) is a pleiotropic cytokine that is involved in numerous biological activities such as hematopoiesis, osteoclastogenesis, neurogenesis and female fertility. IL-11 is obviously a key reagent to study the IL-11 receptors. However, conventional radio-iodination techniques lead to a loss of IL-11 bioactivity. Here, we report the construction and the production of a new recombinant human IL-11 (FP Delta IL-11). In this molecule, a specific phosphorylation site (RRASVA) has been introduced at the N-terminus of rhIL-11. It can be specifically phosphorylated by bovine heart protein kinase and accordingly, easily radiolabeled with (32)P. A high radiological specific activity (250,000 c.p.m x ng(-1) of protein) was obtained with the retention of full biological activity of the protein. The binding of (32)P-labeled FP Delta IL-11 to Ba/F3 cells stably transfected with plasmids encoding human IL-11 receptors alpha and beta chains (IL-11R alpha and gp130) was specific and saturable with a high affinity as determined from Scatchard plot analysis. Availability of this new ligand should prompt further studies on IL-11R structure, expression and regulation.

Co-localization of Rac1 and E-cadherin in human epidermal keratinocytes

The Rac1 small GTP-binding protein is known to be involved in reorganization of the actin cytoskeleton and in regulation of intracellular signal transduction. The assembly and maintenance of cadherin-based cell cell junctions in epidermal keratinocytes is thought to be dependent on activity of Rac1. In this study we have generated green fluorescent protein (GFP)-tagged wild type, dominant negative and constitutively active Rac1 expression vectors and analyzed distribution of Rac1 following microinjection of human SCC12F epidermal keratinocytes. Wild type, dominant negative and constitutively active GFP Rac1 proteins distribute to sites of cell cell adhesion and co-localize with E-cadherin and the catenins. Disruption of cadherin-based junctions by reduction in extracellular calcium concentrations, or by use of antibodies to E-cadherin, results in redistribution of Rac1 away from sites of cell cell interaction but the co-localization with E-cadherin is maintained. In addition, expression of constitutively active GFP Rac1 results in formation of membrane ruffles on the apical surface of cells and intracellular vesicles. Interestingly, co-localization of Rac1 with E-cadherin is maintained in these structures. In contrast to previously published work we find that expression of dominant negative Rac1 neither disrupts cell cell adhesion nor prevents assembly of new cadherin-based adhesion structures.

Interleukin-11 signals through the formation of a hexameric receptor complex

Interleukin-11 (IL-11) is a member of the gp130 family of cytokines. These cytokines drive the assembly of multisubunit receptor complexes, all of which contain at least one molecule of the transmembrane signaling receptor gp130. IL-11 has been shown to induce gp130-dependent signaling through the formation of a high affinity complex with the IL-11 receptor (IL-11R) and gp130. Site-directed mutagenesis studies have identified three distinct receptor binding sites of IL-11, which enable it to form this high affinity receptor complex. Here we present data from immunoprecipitation experiments, using differentially tagged forms of ligand and soluble receptor components, which show that multiple copies of IL-11, IL-11R, and gp130 are present in the receptor complex. Furthermore, it is demonstrated that sites II and III of IL-11 are independent gp130 binding epitopes and that both are essential for gp130 dimerization. We also show that a stable high affinity complex of IL-11, IL-11R, and gp130 can be resolved by nondenaturing polyacrylamide gel electrophoresis, and its composition verified by second dimension denaturing polyacrylamide gel electrophoresis. Results indicate that the three receptor binding sites of IL-11 and the Ig-like domain of gp130 are all essential for this stable receptor complex to be formed. We therefore propose that IL-11 forms a hexameric receptor complex composed of two molecules each of IL-11, IL-11R, and gp130.

Siglec-9, a novel sialic acid binding member of the immunoglobulin superfamily expressed broadly on human blood leukocytes

Here we characterize the properties and expression pattern of Siglec-9 (sialic acid-binding Ig-like lectin-9), a new member of the Siglec subgroup of the immunoglobulin superfamily. A full-length cDNA encoding Siglec-9 was isolated from a dibutyryl cAMP-treated HL-60 cell cDNA library. Siglec-9 is predicted to contain three extracellular immunoglobulin-like domains that comprise an N-terminal V-set domain and two C2-set domains, a transmembrane region and a cytoplasmic tail containing two putative tyrosine-based signaling motifs. Overall, Siglec-9 is approximately 80% identical in amino acid sequence to Siglec-7, suggesting that the genes encoding these two proteins arose relatively recently by gene duplication. Binding assays showed that, similar to Siglec-7, Siglec-9 recognized sialic acid in either the alpha2,3- or alpha2, 6-glycosidic linkage to galactose. Using a specific mAb, Siglec-9 was found to be expressed at high or intermediate levels by monocytes, neutrophils, and a minor population of CD16(+), CD56(-) cells. Weaker expression was observed on approximately 50% of B cells and NK cells and minor subsets of CD8(+) T cells and CD4(+) T cells. These results show that despite their high degree of sequence similarity, Siglec-7 and Siglec-9 have distinct expression profiles.

Leukemia-inhibitory factor-neuroimmune modulator of endocrine function

Leukemia-inhibitory factor (LIF) is a pleiotropic cytokine expressed by multiple tissue types. The LIF receptor shares a common gp130 receptor subunit with the IL-6 cytokine superfamily. LIF signaling is mediated mainly by JAK-STAT (janus-kinase-signal transducer and activator of transcription) pathways and is abrogated by the SOCS (suppressor-of cytokine signaling) and PIAS (protein inhibitors of activated STAT) proteins. In addition to classic hematopoietic and neuronal actions, LIF plays a critical role in several endocrine functions including the utero-placental unit, the hypothalamo-pituitary-adrenal axis, bone cell metabolism, energy homeostasis, and hormonally responsive tumors. This paper reviews recent advances in our understanding of molecular mechanisms regulating LIF expression and action and also provides a systemic overview of LIF-mediated endocrine regulation. Local and systemic LIF serve to integrate multiple developmental and functional cell signals, culminating in maintaining appropriate hormonal and metabolic homeostasis. LIF thus functions as a critical molecular interface between the neuroimmune and endocrine systems.

Receptor recognition by gp130 cytokines

Cytokines of the gp130 family exert their diverse biological effects by formation of stable high affinity transmembrane receptor complexes that are characterized by the presence of the shared transmembrane signalling receptor gp130. Different gp130 ligands form signalling complexes that vary in both composition and stoichiometry. Analysis of the three-dimensional structure of selected ligands and receptor elements indicates that ligands display three topologically conserved receptor recognition epitopes that interact with complementary ligand recognition elements. The composition of the signalling complex and downstream biological responses is defined by the relative affinity of different receptor components for these epitopes. The detailed structure of receptor recognition epitopes indicates that the generation of small molecule cytokine mimetics may be a feasible objective.

The gp130 cytokines interleukin-11 and ciliary neurotropic factor regulate through specific receptors the function and growth of lactosomatotropic and folliculostellate pituitary cell lines

Two of the most potent cytokines regulating anterior pituitary cell function are leukemia inhibitory factor and interleukin-6 (IL-6), which belong to the cytokine receptor family using the common gp130 signal transducer. We studied the actions of two other members of this family, IL-11 and ciliary neurotropic factor (CNTF), on folliculostellate (FS) cells (TtT/GF cell line) and lactosomatotropic cells (GH3 cell line). The messenger RNA (mRNA) for the alpha-chain specific for the IL-11 receptor (1.7 kb) and CNTF receptor (2 kb) are expressed on both cell types. In addition, we detected CNTF receptor mRNA in normal rat anterior pituitary cells. IL-11 (1.25-5 nM) dose dependently stimulated the proliferation of FS cells. CNTF, at doses from 0.4-2 nM, also significantly stimulated the growth of these cells. In addition, both cytokines significantly stimulated proliferation of lactosomatotropic GH3 cells, and CNTF stimulated hormone production (GH and PRL) at 24 h by these cells. At 16-72 h, IL-11 stimulates the secretion of the angiogenic factor vascular endothelial growth factor by FS cells. In addition, both GH3 and FS cells express CNTF mRNA. These data suggest that IL-11 and CNTF may act as growth and regulatory factors in anterior pituitary cells.

Definition of receptor binding sites on human interleukin-11 by molecular modeling-guided mutagenesis

Interleukin-11 (IL-11) belongs to the interleukin-6 (IL-6)-type subfamily of long-chain helical cytokines including IL-6, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), oncostatin M, and cardiotrophin-1, which all share the glycoprotein gp130 as a signal transducing receptor component. IL-11 acts on cells expressing gp130 and the IL-11 receptor (IL-11R) alpha-subunit (IL-11Ralpha). The structural epitopes of IL-11 required for the recruitment of the individual receptor subunits have not yet been defined. Based on the structure of CNTF, a three-dimensional model of human IL-11 was built. Using this model, 10 surface exposed amino acid residues of IL-11 were selected for mutagenesis using analogies to the well-characterized receptor recruitment sites of IL-6, CNTF, and LIF. The respective mutants of human IL-11 were expressed as soluble fusion proteins in bacteria. Their biological activities were determined on HepG2 and Ba/F3-130-11alpha cells. Several mutants with substantially decreased bioactivity and one hyperagonistic mutant were identified and further analyzed with regard to recruitment of IL-11Ralpha and gp130. The low-activity mutant I171D still binds IL-11Ralpha but fails to recruit gp130, whereas the hyperagonistic variant R135E more efficiently engages the IL-11R subunits. The low-activity mutants R190E and L194D failed to bind to IL-11Ralpha. These findings reveal a common mechanism of receptor recruitment in the family of IL-6-type cytokines and offer considerable perspectives for the rational design of IL-11 antagonists and hyperagonists.

Introduction to stem cell biology in vitro. Threshold to the future

Transplantable hematopoietic cells with multilineage reconstituting ability can be quantitated in suspensions of human or murine cells using similar assay procedures. The incorporation into these assays of stringently defined functional endpoints ensures a high degree of specificity for the cells detected. Application of these assays to stem cell-containing suspensions after they have been stimulated for several days with defined cytokines in vitro, or by a mixture of defined and/or undefined factors in vivo, has shown that net amplifications in these populations can be obtained under both circumstances. Such studies have allowed cytokine conditions that support stem cell self-renewal divisions to be identified and have also provided evidence that stem cell regeneration can be manipulated both in vitro and in vivo by altering the molecular milieu of the responding cells. These observations pave the way to future delineation of mechanisms that control the normal behavior, pathology and future clinical exploitation of hematopoietic stem cell populations.

A fusion protein of interleukin-11 and soluble interleukin-11 receptor acts as a superagonist on cells expressing gp130

Interleukin-11 is a hematopoietic cytokine that signals via the signal transducer gp130. Although gp130 is ubiquitously expressed, interleukine-11 responsiveness is restricted to cells that express the interleukine-11 receptor alpha-subunit. The interleukine-11 receptor alpha-subunit can be functionally replaced by its soluble form indicating that the transmembrane and cytoplasmic parts are not required for signal transduction. Here, we show that a recombinant fusion protein of a fragment of the human interleukine-11 receptor alpha-subunit ectodomain linked to human interleukine-11 acts as a superagonist on cells expressing gp130 but lacking the membrane-bound interleukine-11 receptor alpha-subunit. It induces acute phase protein synthesis in hepatoma cells and efficiently promotes proliferation of Ba/F3 cells stably, transfected with gp130. In these bioassays, the fusion protein of a fragment of the human interleukine-11 receptor alpha-subunit ectodomain linked to human interleukine-11 is 50 times more potent than the combination of interleukine-11 and the soluble interleukine-11 receptor alpha-subunit. Thus, our findings support the concept that covalent fusion of two soluble proteins required for receptor activation dramatically increases their bioactivity.

Identification of three distinct receptor binding sites of murine interleukin-11

Interleukin-11 (IL-11) is a member of the gp130 family of cytokines. These cytokines drive the assembly of multisubunit receptor complexes, all of which contain at least one molecule of the transmembrane signaling receptor gp130. A complex of IL-11 and the IL-11 receptor (IL-11R) has been shown to interact with gp130, with high affinity, and to induce gp130- dependent signaling. In this study, we have identified residues crucial for the binding of murine IL-11 (mIL-11) to both the IL-11R and gp130 by examining the activities of mIL-11 mutants in receptor binding and cell proliferation assays. The location of these residues, as predicted from structural studies and a model of IL-11, reveals that mIL-11 has three distinct receptor binding sites. These are structurally and functionally analogous to the previously defined receptor binding sites I, II, and III of interleukin-6 (IL-6). This supports the hypothesis that IL-11 signals via the formation of a hexameric receptor complex and indicates that site III is a generic feature of cytokines that signal via association with gp130.

Trophic effects of cardiotrophin-1 and interleukin-11 on rat dorsal root ganglion neurons in vitro

Cardiotrophin-1 (CT-1) was originally isolated for its hypertrophy inducing effects on cardiac myocytes whereas interleukin-11 (IL-11) was identified due to its ability to stimulate an interleukin-6 (IL-6) dependent plasmocytoma cell line. Both cytokines are structurally and functionally related to a group of factors called neuropoietic cytokines, which also includes IL-6, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), and oncostatin M. These factors have trophic effects on subsets of neurons. In the present study we examined the influence of CT-1 and IL-11 on newborn rat dorsal root ganglion neuron survival in vitro. Mouse CT-1 showed prominent trophic effects that were comparable to those of CNTF and LIF. Mouse IL-11 alone did not enhance neuronal survival, but soluble mouse IL-11 receptor alpha rendered neurons sensitive to IL-11. Surprisingly, soluble IL-11 receptor alpha even had slight neurotrophic effects by itself. These results suggest that CT-1 and IL-11 might also be involved in the physiological regulation of sensory neuron survival. Thus, they might, like CNTF, become tools for the therapeutic intervention in neurodegeneration due to disease, toxicity, and trauma.

Interleukin-6-type cytokine signalling through the gp130/Jak/STAT pathway

The family of cytokines signalling through the common receptor subunit gp130 comprises interleukin (IL)-6, IL-11, leukaemia inhibitory factor, oncostatin M, ciliary neurotrophic factor and cardiotrophin-1. These so-called IL-6-type cytokines play an important role in the regulation of complex cellular processes such as gene activation, proliferation and differentiation. The current knowledge on the signal-transduction mechanisms of these cytokines from the plasma membrane to the nucleus is reviewed. In particular, we focus on the assembly of receptor complexes after ligand binding, the activation of receptor-associated kinases of the Janus family, and the recruitment and phosphorylation of transcription factors of the STAT family, which dimerize, translocate to the nucleus, and bind to enhancer elements of respective target genes leading to transcriptional activation. The important players in the signalling pathway, namely the cytokines and the receptor components, the Janus kinases Jak1, Jak2 and Tyk2, the signal transducers and activators of transcription STAT1 and STAT3 and the tyrosine phosphatase SHP2 [SH2 (Src homology 2) domain-containing tyrosine phosphatase] are introduced and their structural/functional properties are discussed. Furthermore, we review various mechanisms involved in the termination of the IL-6-type cytokine signalling, namely the action of tyrosine phosphatases, proteasome, Jak kinase inhibitors SOCS (suppressor of cytokine signalling), protein inhibitors of activated STATs (PIAS), and internalization of the cytokine receptors via gp130. Although all IL-6-type cytokines signal through the gp130/Jak/STAT pathway, the comparison of their physiological properties shows that they elicit not only similar, but also distinct, biological responses. This is reflected in the different phenotypes of IL-6-type-cytokine knock-out animals.

Important immunoregulatory role of interleukin-11 in the inflammatory process in rheumatoid arthritis

OBJECTIVE

To investigate the possible immunoregulatory role of interleukin-11 (IL-11) in rheumatoid arthritis (RA).

METHODS

IL-11 protein was assayed in RA tissue, and the effect of exogenous IL-11 on neutralization of endogenous IL-11 was investigated with respect to tumor necrosis factor alpha (TNFalpha), matrix metalloproteinase (MMP), and tissue inhibitor of metalloproteinases (TIMP) production.

RESULTS

IL-11 was found in RA synovial membranes, synovial fluids, and blood sera. Blockade of endogenous IL-11 resulted in a 2-fold increase in TNFalpha levels, which increased to 22-fold if endogenous IL-10 was also blocked. Addition of exogenous IL-11 inhibited spontaneous TNFalpha production in RA synovium only in the presence of soluble IL-11 receptor. However, exogenous IL-11 directly inhibited spontaneous MMP-1 and MMP-3 production, and up-regulated TIMP-1 in RA synovial tissue.

CONCLUSION

IL-11 has important endogenous immunoregulatory effects in RA synovium, which suggests that exogenous IL-11 may have therapeutic activity in RA.

Maternal IL-11Ralpha function is required for normal decidua and fetoplacental development in mice

In eutherian mammals, implantation and establishment of the chorioallantoic placenta are essential for embryo development and survival. As a maternal response to implantation, uterine stromal cells proliferate, differentiate, and generate the decidua, which encapsulates the conceptus and forms the maternal part of the placenta. Little is known about decidual functions and the molecular interactions that regulate its development and maintenance. Here we show that the receptor for the cytokine interleukin-11 (IL-11Ralpha) is required specifically for normal establishment of the decidua. Females homozygous for a hypomorphic IL-11Ralpha allele are fertile and their blastocysts implant and elicit the decidual response. Because of reduced cell proliferation, however, only small deciduae form. Mutant deciduae degenerate progressively, and consequently embryo-derived trophoblast cells generate a network of trophoblast giant cells but fail to form a chorioallantoic placenta, indicating that the decidua is essential for normal fetoplacentation. IL-11Ralpha is expressed in the decidua as well as in numerous other tissues and cell types, including the ovary and lymphocytes. The differentiation state and proliferative responses of B and T-lymphocytes in mutant females were normal, and wild-type females carrying IL-11Ralpha mutant ovaries had normal deciduae, suggesting that the decidualization defects do not arise secondarily as a consequence of perturbed IL-11Ralpha signaling defects in lymphoid organs or in the ovary. Therefore, IL-11Ralpha signaling at the implantation site appears to be required for decidua development.

Activation of the signal transducer gp130 by interleukin-11 and interleukin-6 is mediated by similar molecular interactions

The transmembrane glycoprotein gp130 is involved in many cytokine-mediated cellular responses and acts therein as the signal transducing receptor subunit. Interleukin-6 (IL-6) and interleukin-11 (IL-11), in complex with their specific alpha-receptors, homodimerize gp130 and, as a consequence, activate the Janus kinase (Jak)/signal transducer and activator of transcription (STAT) signalling pathway in their target cells. So far, it is not clear whether gp130 is bound to these cytokines and their specific alpha-receptor subunits through identical or different epitopes. In order to study the interaction of IL-11 and IL-11R with human gp130 the soluble form of the recently cloned human IL-11R was expressed in baculovirus-infected insect cells. By a coprecipitation binding-assay it is demonstrated that IL-11 and IL-6 compete for binding to gp130. Using deletion and point mutants of gp130 it is shown that IL-11-IL-11R and IL-6-IL-6R recognize overlapping binding motifs on gp130. Moreover, using well-established Jak-deficient cell lines we demonstrate that STAT activation by IL-11 requires Jak1. Taken together, our data support the concept that IL-6 and IL-11 activate gp130 by very similar molecular mechanisms.

Crystal structure of a cytokine-binding region of gp130

The structure of the cytokine-binding homology region of the cell surface receptor gp130 has been determined by X-ray crystallography at 2.0 A resolution. The beta sandwich structure of the two domains conforms to the topology of the cytokine receptor superfamily. This first structure of an uncomplexed receptor exhibits a similar L-shaped quaternary structure to that of ligand-bound family members and suggests a limited flexibility in relative domain orientation of some 3 degrees. The putative ligand-binding loops are relatively rigid, with a phenylalanine side chain similarly positioned to exposed aromatic residues implicated in ligand binding for other such receptors. The positioning and structure of the N-terminal portion of the polypeptide chain have implications for the structure and function of cytokine receptors, such as gp130, which contain an additional N-terminal immunoglobulin-like domain.

Recombinant Soluble Interleukin-11 (IL-11) Receptor α-Chain Can Act as an IL-11 Antagonist

We have expressed a soluble N-glycosylated form of the murine interleukin-11 (IL-11) receptor α-chain (sIL-11R) and examined signaling in cells expressing the gp130 molecule. In the presence of gp130 but not the transmembrane IL-11R, the sIL-11R mediated IL-11–dependent differentiation of M1 leukemic cells and proliferation in Ba/F3 cells. Early intracellular events stimulated by the sIL-11R including phosphorylation of gp130, STAT 3, and SHP-2 were similar to signaling through the transmembrane IL-11R. IL-11 bound to sIL-11R with low affinity (kd 10 to 50 nmol/L). Binding of sIL-11R to gp130 was IL-11 dependent with intermediate affinity (kd 1.5 to 3.0 nmol/L). However, the concentration of IL-11 required for signaling through the sIL-11R was 10- to 20-fold greater than that required for cells expressing the transmembrane IL-11R and gp130 in the absence of sIL-11R. Furthermore, the sIL-11R was capable of antagonizing the activity of IL-11 when tested on cells expressing the transmembrane IL-11R and gp130. We propose that the observed IL-11 antagonism by the sIL-11R may depend on limiting numbers of gp130 molecules on cells already expressing the transmembrane IL-11R.

Recombinant Soluble Interleukin-11 (IL-11) Receptor α-Chain Can Act as an IL-11 Antagonist

We have expressed a soluble N-glycosylated form of the murine interleukin-11 (IL-11) receptor α-chain (sIL-11R) and examined signaling in cells expressing the gp130 molecule. In the presence of gp130 but not the transmembrane IL-11R, the sIL-11R mediated IL-11–dependent differentiation of M1 leukemic cells and proliferation in Ba/F3 cells. Early intracellular events stimulated by the sIL-11R including phosphorylation of gp130, STAT 3, and SHP-2 were similar to signaling through the transmembrane IL-11R. IL-11 bound to sIL-11R with low affinity (kd 10 to 50 nmol/L). Binding of sIL-11R to gp130 was IL-11 dependent with intermediate affinity (kd 1.5 to 3.0 nmol/L). However, the concentration of IL-11 required for signaling through the sIL-11R was 10- to 20-fold greater than that required for cells expressing the transmembrane IL-11R and gp130 in the absence of sIL-11R. Furthermore, the sIL-11R was capable of antagonizing the activity of IL-11 when tested on cells expressing the transmembrane IL-11R and gp130. We propose that the observed IL-11 antagonism by the sIL-11R may depend on limiting numbers of gp130 molecules on cells already expressing the transmembrane IL-11R.

Cloning and expression of an alternatively spliced mRNA encoding a soluble form of the human interleukin-6 signal transducer gp130

The membrane-bound gp130 glycoprotein acts as an affinity converting and signal transducing receptor (R) for interleukin-6 and several other cytokines. In this work, we RT-PCR amplified gp130 cDNA using primers flanking the sequence encoding the transmembrane domain of gp130. We observed in blood mononuclear cells, in addition to the expected 333-bp length fragment, a second major band of 418 bp. Sequencing of the 418-bp fragment and its genomic counterpart showed a new 85-bp exon located in the sequence encoding the extracellular region of the gp130 protein. This exon is most likely due to alternative splicing and leads to a frame-shift resulting in a stop-codon 1 bp before the transmembrane coding region. Correspondingly, supernatants from chinese hamster ovary cells transfected with this cDNA contained 4-5 times more soluble (s) gp130 than supernatants from cells transfected with a cDNA encoding the membrane-bound gp130 protein. Both gp130 and alternatively spliced sgp130 were also transcribed by the myeloma cell lines XG-1, XG-2, XG-4, XG-4CNTF XG-6, XG-7, XG-9, XG-10, U266 and RPMI 8226. However, XG-4A cells derived from XG-4 cells, but growing independently of exogenous IL-6, did not transcribe sgp130 mRNA. A possible interference with intracrine stimulatory factors by alternatively spliced sgp130 needs to be further investigated.

Production and characterization of monoclonal antibodies against the leukemia inhibitory factor low affinity receptor, gp190

Leukemia inhibitory factor (LIF), oncostatin-M (OSM), ciliary neurotrophic factor (CNTF) and cardiotrophin-1 (CT1) act through transmembrane receptors which share the gp190 glycoprotein chain. The understanding of its involvement in the biology of these cytokines is of importance since these systems have recently been shown to participate in major inflammatory and neoplastic processes such as myelomatosis (Rose-John, S., Heinrich, P.C., 1994. Soluble receptors for cytokines and growth factors: generation and biological function. Biochem. J. 300, 281). In addition, this family of receptors also shares the gp130 transducing chain, with the IL6 and IL11 receptors. Because IL6 and gp130 were the first members to be discovered, most of the available reagents are directed at them. In this respect, monoclonal antibodies have played a major role in elucidating these receptor/ligand interactions and exploring the pathophysiological aspects of their biology. So far, no such reagents have been described for the gp190. We now report the production and characterization of 16 monoclonal antibodies directed against human gp190. They were obtained using recombinant chimeric or truncated proteins produced in a eukaryotic CHO cell line. One was able to block the biological activity of LIF. Because gp190 comprises two hematopoietin binding domains, crude epitope mapping was possible using the same reagents. While more of these antibodies are required, the present set validate the technological approach used for their preparation and should improve our understanding of this class of cytokines.

Two differentially expressed interleukin-11 receptor genes in the mouse genome

Interleukin-11 (IL-11) is a multifunctional cytokine involved in the regulation of cell proliferation and differentiation in a variety of cell types and tissues in vitro and in vivo. The effects of IL-11 were shown to be mediated by the IL-11 receptor (hereafter referred to as IL-11 R alpha), which is a ligand-binding subunit and provides ligand specificity in a functional multimeric signal-transduction complex with gp130. Here we show that the mouse genome contains a second gene encoding an IL-11-binding protein, referred to as IL-11R beta. The structure of the IL-11R beta gene is highly similar to that of IL-11R alpha, and IL-11R beta exhibits 99% sequence identity with IL-11R alpha at the amino acid level. IL-11R beta is co-expressed with IL-11R alpha, albeit at lower levels, in embryos and in various adult tissues. IL-11R beta transcripts are abundant in testis, and, in contrast with IL-11R alpha, absent from skeletal muscle. IL-11R beta expressed in vitro binds IL-11 with high affinity, suggesting that the mouse genome contains a second functional IL-11R.