Organization and chromosomal localization of the human interleukin 5 receptor alpha-chain gene

The gene for the hIL-5R alpha subunit, which is present in a single copy in the human genome, has been analysed in detail. It is located on chromosome 3 in the region 3p26. The gene organization reflects its relationship to the cytokine/haematopoietin receptor superfamily. Three introns are located in the 5' untranslated region. The subsequent exons determine the functional domains of the hIL-5R alpha protein: the signal peptide, three fibronectin type III-like (FN-like) modules, each built up by two exons, the membrane anchor and two exons forming the cytoplasmic tail, the first of which contains the proline cluster region. In addition, a specific exon generating a soluble isoform is located before the membrane anchor exon. This specific exon contains an in frame TAA stop codon, followed by a polyadenylation signal. Hence, a normal splicing event leads to a soluble IL-5R alpha variant, whereas alternative splicing is required for cell membrane anchoring. A second area of alternative splicing is found in the 5' leader sequence, and possibly relates to the presence of short open reading frames preceding the main ATG. All intron-exon junctions meet the GT-AG rule. The gene structures of all cytokine/haematopoietin receptors documented so far have also been compared with respect to intron phasing. This shows that all introns between the FN-III-like modules are of the +1 type, but in addition, splice sites within the Cys-module and WS-WS-module are invariably of the +2 and 0 type, respectively.

Molecular basis of the membrane-anchored and two soluble isoforms of the human interleukin 5 receptor alpha subunit

By use of a 3' extension PCR strategy, cDNA clones were isolated spanning the transmembrane region and a complete cytoplasmic domain of the human interleukin 5 receptor alpha subunit (hIL5R alpha). These cDNAs differ from previously isolated clones encoding a soluble hIL5R alpha form by a sequence switch at position 1243. When expressed in COS-1 cells, only low-affinity binding of 125I-labeled human interleukin 5 was observed. Coexpression of the hIL5R beta chain led to a 2-fold increase in binding affinity. In addition, this same cloning strategy allowed us to identify a putative second soluble isoform of hIL5R alpha. Genomic data revealed that the two soluble variants arise from either a "normal" splicing event or from the absence of splicing, whereas synthesis of the membrane-anchored form requires alternative splicing.

Precursor frequency analysis of human cytolytic T lymphocytes directed against autologous melanoma cells

Limiting numbers of peripheral-blood mononuclear cells (PBMC) from melanoma patients were stimulated with irradiated autologous tumor cells in the presence of interleukins-2 and -4 and in the absence of feeder cells. The responder cells were restimulated every week. After 2 to 4 weeks, the microcultures were tested for their lytic activity against the autologous tumor cells. Significant lysis of the tumor cells was observed with a fraction of these microcultures, whereas no lysis was observed with control microcultures seeded without stimulator melanoma cells. Because our aim was to measure the precursor frequency of CTL showing specificity for the tumor, and not that of NK-like effectors that were also capable of lysing the melanoma cells, we used cold-target inhibition with an excess of NK target K562 to inhibit the NK-like activity. Microcultures whose lysis on the tumor cells was not abolished by K562 competition were observed. The specificity of these CTL clones was confirmed by the absence of lytic activity on autologous T-cell blasts. The numbers of microcultures with anti-tumor CTL activity fitted the zero-order of the Poisson distribution equation, indicating that they resulted from the activity of single T-cell clones. The frequency of anti-tumor CTL precursor cells (CTL-P) of 7 melanoma patients ranged from 1/900 to 1/33,000. Frequencies of anti-tumoral CTL-P were higher and NK-like effectors were less frequent when sorted CD8+ T lymphocytes were used as responder cells.

Characterization of the murine IL-5 receptor complex with the use of a panel of monoclonal antibodies. Relationship to the murine IL-3 receptor

To obtain mAb against the murine IL-5R (mIL-5R), Wistar rats were immunized with B13 cells, a murine Ly-1+ (CD5+) pre-B cell line which is dependent on IL-3 or IL-5 for its growth. A first group of six mAb could immunoprecipitate, from detergent-lysed B13 cells, a 60-kDa polypeptide (p60) corresponding to the recently cloned mIL-5R alpha-chain. A second group of three mAb was able to immunoprecipitate a protein doublet of 130 to 140 kDa (p130 and p140) corresponding to the previously characterized mIL-3R and mIL-3R-like polypeptide, respectively. One mAb (25C9) specifically bound the p130 polypeptide only. Here we show that: 1) mAb directed against the mIL-5R p60 component completely block IL-5 binding; 2) mAb recognizing the p130-p140 doublet interfere with both IL-3 and IL-5 binding; 3) mAb recognizing p130-p140 block the high affinity binding of IL-5 and hence the high affinity mIL-5R consists of the association of the p60 and p130 and/or p140 component; 4) one particular mAb, 25C9, which binds only to the p130 polypeptide, interferes with only IL-3 binding, and has no effect on the binding of IL-5. These results on binding were corroborated by a biologic assay based on the cytokine-dependent proliferation of B13 cells. The results presented here support a model for the mIL-5R consisting of the alpha-chain (p60) associated with the p140 (IL-3R-like), whereas the p130 (IL-3R) is not involved in the IL-5R complex.

Characterization of the murine IL-5 receptor complex with the use of a panel of monoclonal antibodies. Relationship to the murine IL-3 receptor

To obtain mAb against the murine IL-5R (mIL-5R), Wistar rats were immunized with B13 cells, a murine Ly-1+ (CD5+) pre-B cell line which is dependent on IL-3 or IL-5 for its growth. A first group of six mAb could immunoprecipitate, from detergent-lysed B13 cells, a 60-kDa polypeptide (p60) corresponding to the recently cloned mIL-5R alpha-chain. A second group of three mAb was able to immunoprecipitate a protein doublet of 130 to 140 kDa (p130 and p140) corresponding to the previously characterized mIL-3R and mIL-3R-like polypeptide, respectively. One mAb (25C9) specifically bound the p130 polypeptide only. Here we show that: 1) mAb directed against the mIL-5R p60 component completely block IL-5 binding; 2) mAb recognizing the p130-p140 doublet interfere with both IL-3 and IL-5 binding; 3) mAb recognizing p130-p140 block the high affinity binding of IL-5 and hence the high affinity mIL-5R consists of the association of the p60 and p130 and/or p140 component; 4) one particular mAb, 25C9, which binds only to the p130 polypeptide, interferes with only IL-3 binding, and has no effect on the binding of IL-5. These results on binding were corroborated by a biologic assay based on the cytokine-dependent proliferation of B13 cells. The results presented here support a model for the mIL-5R consisting of the alpha-chain (p60) associated with the p140 (IL-3R-like), whereas the p130 (IL-3R) is not involved in the IL-5R complex.

A human high affinity interleukin-5 receptor (IL5R) is composed of an IL5-specific alpha chain and a beta chain shared with the receptor for GM-CSF

cDNA clones encoding two receptor proteins involved in the binding of human interleukin 5 (hIL5) have been isolated. A first class codes for an IL5-specific chain (hIL5R alpha). The major transcript of this receptor gene, as analyzed in both HL-60 eosinophilic cells and eosinophilic myelocytes grown from cord blood, encodes a secreted form of this receptor. This soluble hIL5R alpha has antagonistic properties. A second component of the hIL5R is found to be identical to the beta chain of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) high affinity receptor. The finding that IL5 and GM-CSF share a receptor subunit provides a molecular basis for the observation that these cytokines can partially interfere with each other's binding and have highly overlapping biological activities on eosinophils.

Molecular basis of a high affinity murine interleukin-5 receptor

The mouse interleukin-5 receptor (mIL-5R) consists of two components one of which, the mIL-5R alpha-chain, binds mIL-5 with low affinity. Recently we demonstrated that monoclonal antibodies (Mabs) recognizing the second mIL-5R beta-chain, immunoprecipitate a p130-140 protein doublet which corresponds to the mIL-3R and the mIL-3R-like protein, the latter chain for which so far no ligand has been identified. In this study we show that a high affinity mIL-5R can be reconstituted on COS1 cells by co-expression of the mIL-5R alpha-chain with the mIL-3R-like protein (beta-chain). Cross-linking of 125I-labeled mIL-5 to the COS1 cells co-transfected with both cDNAs revealed the same pattern as in B13 cells, i.e. two proteins of 60 and 130 kd which correspond to the low affinity mIL-5R alpha-chain and the mIL-3R-like protein, respectively. The dissociation rate of mIL-5 from this reconstituted high affinity site was lower than that of the low affinity site, whereas the association rate was unchanged. Nonetheless, the apparent dissociation constant (Kd) for this reconstituted receptor was still 10-fold higher than the Kd observed for B13 cells. Although the mIL-3R is greater than 90% homologous to the mIL-3R-like protein, no increase in affinity for mIL-5 was detected on COS1 cells co-transfected with the cDNAs for the mIL-5R alpha-chain and the mIL-3R protein.

Amino acid sequence analysis of a mouse interleukin 5 receptor protein reveals homology with a mouse interleukin 3 receptor protein

A polypeptide chain for the mouse interleukin 5 receptor (IL5R) was purified from detergent-lysed B13 cells, a mouse IL5-dependent pre-B cell line. Purification was by a single immunoaffinity chromatographic step using an anti-mouse IL5R monoclonal antibody, R52. Internal amino acid sequence was obtained from four trypsin-generated peptides. All peptides were found to be present in the published amino acid sequence of a mouse IL3R and the mouse IL3R-like protein deduced from the cDNA. This indicates that the mouse IL5R and the mouse IL3R have a homologous polypeptide in common and suggests that the specificity of these lymphokine receptors is mainly generated by association with another ligand-specific polypeptide chain.

Expression of the murine interleukin-5 receptor on Xenopus laevis oocytes

In this study we describe the use of Xenopus laevis oocytes for the detection of mRNA coding for a murine interleukin-5 (mI15) receptor. When injected with sucrose gradient fractionated polyA+ RNA derived from the murine 115-dependent pre B cell line B13, these oocytes could specifically bind 35S-methionine labeled mI15. A size of approximately 4000 nucleotides (25S) was estimated for the mRNA corresponding to the mIL5-binding activity. This binding was not blocked by a monoclonal antibody R52 specific for the MI15-receptor, suggesting that the oocytes express a different form of this receptor.

Characterization of interleukin 5 receptors on eosinophilic sublines from human promyelocytic leukemia (HL-60) cells

The T cell product interleukin 5 (IL-5) has been shown to be a key factor in the development and the maturation of the eosinophilic cell lineage. We report here on the detection of human IL-5 receptors on eosinophilic sublines of the promyelocytic leukemia HL-60. Sodium butyrate, which initiates differentiation to mature eosinophils, also induces the appearance of high affinity (Kd 1-5 X 10(-11) M) IL-5 binding sites on these cells. The receptors are specific for IL-5, since binding of radiolabeled ligand can only be inhibited with homologous or murine IL-5 and not by other cytokines. We further show that the receptors are functional, since IL-5 can stimulate the proliferation of these cells. Affinity crosslinking of surface-bound 125I human IL-5 or 35S mouse IL-5 identified two membrane polypeptides of approximately 60 and approximately 130 kD to which IL-5 is closely associated. The presence of granulocyte/macrophage-colony-stimulating factor or tumor necrosis factor during butyrate induction decreased the expression of IL-5 binding sites compared with control cultures. The identification and characterization of human IL-5 receptors on HL-60 sublines should provide new insight into the role of this cytokine in eosinophil differentiation.

Restrictive dermopathy with distinct morphological abnormalities

A newborn child is described with the fetal hypokinesia sequence as a consequence of a restrictive dermopathy. Remarkable findings in this infant were neonatal teeth and survival till age 4 months. Ultrastructural examination of the skin showed thin epidermis and absence of elastic fibres.

Expression of human and murine interleukin-5 in eukaryotic systems

A cDNA coding for murine interleukin-5 (IL-5) was isolated from the EL4.ExC5 cell line. With the exception of a single amino acid substitution at position 79 (Arg----His), it is identical to a published sequence. The coding sequence for human IL-5 was synthesized chemically, allowing the introduction of strategically located restriction enzyme cleavage sites. Both cDNAs were expressed in various eukaryotic systems. Deletion of the 3' untranslated region of the murine IL-5 gene led to a 5- to 10-fold increase in expression in Xenopus laevis oocytes and in NIH-3T3 cells. The highest production, however, was obtained in Sf9 cells using a baculovirus vector. Human IL-5 was obtained from transformed Saccharomyces cerevisiae as a secreted, mature form using an in-frame fusion to the leader sequence of alpha-mating type factor, and was purified to homogeneity. In all cases mentioned, IL-5 was found to be glycosylated, and its biological activity was dependent on a 40- to 50-kD homodimer configuration, linked together by disulfide bridges. Deglycosylation did not affect the biological activity. Recombinant human IL-5 is biologically active on some human B-CLL cells (proliferation in the presence of IL-2) and on murine BCl1 cells (proliferation) at a low specific activity (about 1-2 x 10(3) U/mg) and on human eosinophils (eosinophil peroxidase assay) at a high specific activity (at least 5 x 10(6) U/mg). Recombinant murine IL-5 from Sf9 cells has a specific activity of 1-2 x 10(7) U/mg in the BCl1 proliferation assay. An additive effect is seen in the presence of murine granulocyte-macrophage colony-stimulating factor (GM-CSF) and a synergistic effect in the presence of murine IL-4.

Purification of human interleukin-4 produced in Escherichia coli

An interleukin-4 (IL4)-encoding cDNA isolated from human splenocytes was used to construct an expression plasmid that directs a high-level synthesis of mature IL4 protein in Escherichia coli. The expression was under the control of the major leftward promoter, pL, of phage lambda and the phage Mu ribosome-binding site. The IL4 protein was present as insoluble inclusion bodies in the bacterial extract. The IL4 could be solubilized in 5 M MgCl2 and was purified to homogeneity by several chromatographic steps. The yield of protein from bacteria ranged between 3 and 5 mg of IL4 protein per gram of wet cells. The specific activity of the recombinant human IL4 was about the same as that of the natural product.

Interleukin 1 alpha acts as an autocrine growth factor for RPMI 1788, an Epstein-Barr virus-transformed human B cell line

The Epstein-Barr virus-transformed B cell line RPMI 1788 constitutively produces autocrine growth factors with molecular masses of 17 kDa, 24 kDa and 35 kDa. All three molecular forms were completely neutralized with anti-interleukin (IL) 1 alpha antiserum. Although IL 1 alpha and IL 1 beta mRNA were both equally detectable by Northern blotting, no IL 1 beta activity was found in partially purified RPMI 1788 supernatant. The growth of low density-seeded RPMI 1788 cells is specifically dependent on the presence of either IL 1 alpha or IL 1 beta. Since no other cytokine was found to be capable of sustaining proliferation, this cell line is suitable for the identification and quantification of IL 1, even in the presence of other cytokines.

Slippage of DNA polymerase I during synthesis of ds-cDNA

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Production of stable cytolytic T-cell clones directed against autologous human melanoma

We have attempted to optimize the production of stable human cytolytic T lymphocyte clones directed against autologous melanoma cell lines. MLTC were restimulated every week with irradiated melanoma cells in medium containing human serum and IL-2. After 21 to 35 days, in 5 out of 6 patients, these cultures expressed a preferential cytolytic activity against the autologous melanoma cells, as compared to autologous EBV-B cells or NK target K562. Limiting dilution of MLTC responder cells was performed at times varying from days 7 to 28, in medium containing IL-2 and allogeneic EBV-B cells as feeders. Approximately 1% of these responder cells gave rise to CTL clones that lysed the autologous melanoma cells, but did not lyse K562 or autologous B cells. It was possible to maintain in culture for several months a large number of CTL clones that retained this specificity with high activity, and multiplied more than 5-fold every week. Some of these CTL clones were dependent on the presence of the autologous melanoma cells for their growth. With one melanoma, the use of autologous CTL clones made it possible to identify 3 different antigens on the tumor cells.

Structural studies of the carbohydrate chains of human gamma-interferon

Human gamma-interferon (IFN-gamma) was prepared biotechnologically using Chinese hamster ovary cells. These cells were shown to be able to produce glycosylated IFN-gamma. Sugar analysis revealed the presence of Man, Gal, GlcNAc, NeuAc and Fuc residues in a molar ratio of 3.8:2.0:3.5:0.6:0.4 suggesting the occurrence of N-glycosidically linked N-acetyllactosamine type of carbohydrate chains. For structure determination of these chains, the glycoprotein was subjected to the hydrazinolysis procedure, yielding oligosaccharide-alditols. The latter compounds were analysed by 500-MHz 1H-NMR spectroscopy. The carbohydrate material was found to consist of biantennary structures, exhibiting microheterogeneity as to the terminal sialic acids and the core Fuc residue: (Formula: see text). As similar carbohydrates are present on several human secreted proteins, this glycosyl group is not expected to be immunogenic in man. It remains to be established to what extent the carbohydrate chains of this biotechnologically produced IFN-gamma are identical to those of naturally occurring human IFN-gamma.

Cloning and structure of a mouse interleukin-2 chromosomal gene

Using non-stringent hybridization with a human interleukin-2 cDNA probe, we have isolated recombinant phages from a mouse genomic DNA library cloned in the EMBL3 phage. The sequence and organization of the mouse interleukin-2 (IL-2) gene was determined. By comparison with the human IL-2 sequence, three introns can be identified with lengths of 99, +/- 2 400, and +/- 1 900 base pairs, respectively. The mouse IL-2 gene codes for a polypeptide of 169 amino acids and contains a putative signal peptide of 20 amino acids. The homology to the human interleukin-2 is 72% at the nucleotide level in the coding part and 65% at the amino acid level. An extraordinary sequence, consisting of 12 consecutive CAG codons coding for glutamine, is found in the first exon.

Interferon-gamma modulates HLA class II antigen expression on cultured human thymic epithelial cells

Cultures of human thymic epithelial cells (TEC) were tested for the expression of HLA class I (A, B, C) and class II (DR and DC) antigens by indirect immunofluorescence. The epithelial nature of the cells was proven by using an antikeratin antiserum. A high level of expression (close to 100% positive cells) of HLA class I antigens was observed on TEC at the beginning of the culture and remained unchanged for up to 12 days. In contrast, HLA class II antigen expression (85% DR+ and 75% DC+ cells on day 2) decreased gradually and reached very low levels (less than 5% DR+ or DC+) by day 7 of culture. This loss of class II antigen expression was not seen when cultures were performed in the presence of supernatants from activated T cells containing interferon-gamma (IFN-gamma). Furthermore, the presence of recombinant IFN-gamma (rIFN-gamma) in the medium from the onset of culture maintained HLA-DR and DC antigen expression on a high number of cells (comparable to that observed on day 2 of culture). A large percentage of rIFN-gamma-treated cells also showed intracytoplasmic HLA-DR antigen expression. Addition of rIFN-gamma at various times after the onset of the culture led to a reinduction of DR and DC antigen expression. This effect of rIFN-gamma was observed in 48 hr with concentrations as low as 10 IU/ml and was apparently specific for this IFN species, in that rIFN-alpha was unable to modify HLA class II antigen expression at concentrations up to 1000 IU/ml. The increased expression of HLA class II antigen was truly due to induction in individual TEC, rather than selection of class II-positive cells, because induction under the influence of IFN-gamma was reversible and occurred in the absence of proliferation in mitomycin-treated or gamma-irradiated cultures. Our results indicate that synthesis and membrane expression of class II HLA antigens are enhanced by IFN-gamma in TEC cultures. This finding raises the possibility that IFN-gamma participates in the mechanisms that assure the permanent expression of DR and DC antigens observed in TEC in vivo, with potentially important functional consequences in terms of education for self recognition.

Interferon-gamma modulates HLA class II antigen expression on cultured human thymic epithelial cells

Cultures of human thymic epithelial cells (TEC) were tested for the expression of HLA class I (A, B, C) and class II (DR and DC) antigens by indirect immunofluorescence. The epithelial nature of the cells was proven by using an antikeratin antiserum. A high level of expression (close to 100% positive cells) of HLA class I antigens was observed on TEC at the beginning of the culture and remained unchanged for up to 12 days. In contrast, HLA class II antigen expression (85% DR+ and 75% DC+ cells on day 2) decreased gradually and reached very low levels (less than 5% DR+ or DC+) by day 7 of culture. This loss of class II antigen expression was not seen when cultures were performed in the presence of supernatants from activated T cells containing interferon-gamma (IFN-gamma). Furthermore, the presence of recombinant IFN-gamma (rIFN-gamma) in the medium from the onset of culture maintained HLA-DR and DC antigen expression on a high number of cells (comparable to that observed on day 2 of culture). A large percentage of rIFN-gamma-treated cells also showed intracytoplasmic HLA-DR antigen expression. Addition of rIFN-gamma at various times after the onset of the culture led to a reinduction of DR and DC antigen expression. This effect of rIFN-gamma was observed in 48 hr with concentrations as low as 10 IU/ml and was apparently specific for this IFN species, in that rIFN-alpha was unable to modify HLA class II antigen expression at concentrations up to 1000 IU/ml. The increased expression of HLA class II antigen was truly due to induction in individual TEC, rather than selection of class II-positive cells, because induction under the influence of IFN-gamma was reversible and occurred in the absence of proliferation in mitomycin-treated or gamma-irradiated cultures. Our results indicate that synthesis and membrane expression of class II HLA antigens are enhanced by IFN-gamma in TEC cultures. This finding raises the possibility that IFN-gamma participates in the mechanisms that assure the permanent expression of DR and DC antigens observed in TEC in vivo, with potentially important functional consequences in terms of education for self recognition.

Binding of unglycosylated and glycosylated human recombinant interferon-gamma to cellular receptors

Recombinant human interferons (IFNs), either unglycosylated produced in E. coli (rIFN-gamma) or glycosylated produced in CHO cells (g-rIFN-gamma), were labeled with 125I to similar specific activities to study their interaction with cell-surface receptors. When analyzed by gel electrophoresis, rIFN-gamma run as a single polypeptide of Mr 15,000-17,000, whereas g-rIFN-gamma separated into three components of Mr 20,000, 22,000, and 43,000, which corresponded to the known size of the two monomeric and one dimeric forms of glycosylated natural IFN-gamma. The binding of the two species of 125I-IFN-gamma was competed equally by rIFN-gamma in competition displacement experiments with Daudi cells, indicating that these IFNs bind with similar high affinity to the same receptors. KD values of 1.25 X 10(-10) and 2.5 X 10(-10) M were determined for g-rIFN-gamma and rIFN-gamma, respectively. This relatively small difference in KD does not apparently result in a detectable difference in biological activity, as measured by the increase in 2',5'-oligo(A) synthetase activity in IFN-treated HeLa and A549 cells. These results indicate that glycosylation of IFN-gamma does not play a significant role in its interaction with cellular receptors and in the induction of a biological response.

Recombinant interleukin 2 induces immunoglobulin secretion in Staphylococcus aureus Cowan strain I activated human B-cells

Human B-cells, exhaustively depleted for T-cells, were activated with Staphylococcus aureus Cowan strain I (SAC) and responded to recombinant human interleukin 2 (rIL2) by secretion of immunoglobulin (Ig), as measured by a protein A hemolytic plaque assay. The rIL2, however, had to be present early, since addition later than 24 h after SAC-activation of the B-cells reduced the response to background levels. No clear dose response was observed and Ig-secreting cells (ISC) could be induced even with rIL2 at 0.5 U/ml. The monoclonal antibody anti-TAC prevented the rIL2-promoted induction of ISC. Ig production could be induced in SAC-activated cultures with supernatants of Xenopus laevis oocytes injected with sucrose-gradient-fractionated poly(A+) RNA derived from a stimulated human spleen cell culture. This activity coincided with the IL2 mRNA activity and was well separated from the interferon-gamma mRNA activity. Our results suggest that IL2 is not only a B-cell growth factor but also promotes the differentiation of activated human B-cells towards Ig secretion.