Structure-function relationship of tumour necrosis factor and its mechanism of action

We have cloned the cDNAs of both human and mouse TNF and expressed them to high efficiency in Escherichia coli. Many transformed cell lines are sensitive to the cytotoxic action of TNF, especially in the presence of gamma-interferon, whereas normal cells either are unaffected or respond mitogenically. A number of human-mouse chimeric TNF genes have been constructed and expressed. All show biological activity but none of the chimeric proteins is neutralized by monoclonal antibodies to TNF. TNF has potent antitumour activity in nude mice carrying human xenografts or in mice bearing syngeneic tumours. In some systems direct effects can be demonstrated (in combination with species-specific gamma-interferon) but in others TNF acts indirectly. Combination of TNF with cytostatic drugs can also be effective in curing in vivo. The major limitation of the use of TNF is its toxicity. On many cell types TNF has an action similar to interleukin 1 (IL-1). At least some of the secondary, intracellular events may be identical for the two effectors. A possible mechanism of action of TNF is the release and metabolism of polyunsaturated fatty acids, which would explain the synthesis of prostaglandins and leukotrienes by many cell types after TNF treatment. The activation of the phospholipase can be blocked by corticoids. Some protease inhibitors protect cells from TNF-induced cytotoxicity but the target of these inhibitors has not been identified. Several genes are switched on by TNF (and by IL-1), including the gene for the 26 kDa protein recently identified as B cell stimulation factor 2. Events preceding death in rats include hypothermia, hypotension, acidosis and hypoglycaemia. All these effects can be largely eliminated by indomethacin pretreatment, with a resulting improvement in survival. As indomethacin does not inhibit the cytotoxic action of TNF on malignant cells it may form the basis for improved treatment protocols.

Isolation and characterization of a human fibroblast interferon gene and its expression in Escherichia coli

Human fibroblasts were induced for interferon synthesis, and the mRNA coding for interferon was partially purified. On this basis, double-stranded DNA copies were synthesized enzymatically and were inserted into cloning vehicles. A large collection of colonies containing chimeric plasmids was obtained. An RNA selection method was used for the identification of several individual clones containing the human fibroblast interferon (IFN-beta) cDNA. From the nucleotide sequence of the cloned structural gene, the primary structure of the mRNA and, hence, of the protein itself was deduced. IFN-beta is a polypeptide 166 amino acids long and contains a single site for N-glycosylation; IFM-beta is normally made as a preinterferon containing a signal sequence that is 21 amino acids long. The interferon gene was inserted into an expression plasmid under thermoinducible control of the phage lambda PL promoter. this allowed the synthesis of polypeptides in the bacteria, which for all physicochemical, biological, and immunologic properties tested closely resembled authentic IFN-beta.

Slippage of DNA polymerase I during synthesis of ds-cDNA

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Structure/function analysis of human interleukin 5 and its receptor

We have performed a detailed structure-function analysis of human interleukin 5 (hIL5) and its receptor. By testing a hIL5 mutant panel in a solid phase binding assay and a proliferation assay using hIL5 dependent cell-lines, areas on hIL5 involved in either the receptor alpha-subunit interaction or in receptor activation were identified. Epitope mapping data of a neutralizing and a non-neutralizing monoclonal antibody were in agreement with the mutant analysis. hIL5 binding areas on the IL5R alpha-subunit were identified by interspecies chimaera analysis. Finally, hIL5 mutants with reduced receptor activation potential have antagonistic properties.

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.

Tumor necrosis factor induces acute phase proteins in rats

Inoculation of WAG rats with recombinant mouse tumor necrosis factor results in a rapid and marked increase in several acute phase proteins in the serum (haptoglobin, alpha 1 acid glycoprotein, alpha 2 macroglobulin) and in the plasma (fibrinogen). We conclude that TNF may play an important role in the inflammatory response in vivo and possibly in the pathogenesis of inflammatory disorders.

[Bronchocele. A radiological study from 5 cases (author's transl)]

Bronchocele present a characteristic radiological appearance. Their significance varies according to the clinical context:--a picture of diffuse bronchopathy with mucoid impaction would suggest a medical treatment;--in the absence of any bronchopathy the X-ray should seek a under-jacent lesion which would respond to surgery.

[Critical evaluation of non-biological complementary examinations of the biliary tract before deciding on therapy (author's transl)]

A critical evaluation of non-biological complementary examinations of the biliary tract was conducted to assess their value when deciding on therapy. The published literature was reviewed, and the sensitivity and specificity of the different methods presented, emphasis being placed on the primary investigations of ultrasonography and oral and intravenous biligraphy. Secondary exploratory procedures (transparietal cholangiography, retrograde endoscopy with cholangiography and pancreatography, scintigraphy, gallbladder infusion parietography, scanography, and arteriography) are defined and their value discussed. Published data suggest that ultrasonography should be the initial investigation, this often being sufficient to enable suitable therapy to be chosen. Only approximately 5 p. cent of patients are unable to benefit from gallbladder exploration, and these require conventional radiological examinations before deciding on therapy.

Recombinant soluble human interleukin-5 (hIL-5) receptor molecules. Cross-linking and stoichiometry of binding to IL-5

Recombinant soluble human interleukin-5 receptor alpha (shIL-5R alpha) has been expressed in COS-1 cells and in baculovirus-infected cells. The protein was purified from the supernatant by chromatography on concanavalin A-Sepharose, MonoQ, and a final gel filtration step. A chimeric fusion receptor protein (hIL-5R alpha-h gamma 3) was constructed by fusion of the cDNA corresponding to the shIL-5R alpha to the cDNA corresponding to the Fc part of the human IgG C gamma 3 chain, and was expressed in baculovirus-infected insect cells. The chimeric receptor was secreted as a disulfide-linked homodimer, and was purified by protein G affinity chromatography. In a solid-phase binding assay the shIL-5R alpha and the bivalent hIL-5R alpha-h gamma 3 were found to bind hIL-5 with a similar affinity, corresponding to the membrane-bound, low affinity hIL-5R alpha. SDS-polyacrylamide gel electrophoresis of shIL-5R alpha cross-linked to radiolabeled hIL-5, suggested that one shIL-5R alpha molecule binds to one hIL-5 homodimer molecule. Gel filtration studies of the complex formed between the shIL-5R alpha and hIL-5 pointed toward the same stoichiometry of binding. The formation of such a complex could be observed by electrophoresis in native gels. Immunoaffinity chromatography using a non-neutralizing monoclonal antibody directed against hIL-5, followed by size column chromatography, allowed the purification of the complex. The data obtained from the amino acid analysis of the constituents of the complex blotted from an SDS-polyacrylamide gel, and from the amino acid composition of the complex blotted from a native polyacrylamide gel, provided direct evidence that the shIL-5R alpha binds the hIL-5 dimer in a 1:1 ratio.

Toxic effects of recombinant tumor necrosis factor in suckling mice. Comparisons with interferon alpha/beta

Newborn Swiss and A2G mice were given daily subcutaneous injections for 1 week of highly purified recombinant mouse tumor necrosis factor (TNF) or mouse interferon alpha/beta. Both treatments resulted in inhibition of growth of suckling mice and severe fatty changes and necrosis in the liver. The simultaneous injection of polyclonal antibody to interferon alpha/beta abrogated the effects of interferon but did not block the effects induced by TNF. The kidneys of TNF-treated suckling mice could be distinguished from interferon-treated mice by the absence of glomerular basement membrane abnormalities and the presence of numerous rounded eosinophilic hyaline granules within the cytoplasm of the proximal tubules. Treatment of suckling mice with TNF and interferon alpha/beta induced similar changes in the spleen and thymus. Interferon treatment of suckling A2G mice resulted in the appearance of pulmonary cysts, which were not observed in TNF-treated mice. It is concluded that the pattern of lesions induced in suckling mice by mouse TNF is both similar and different from that induced by mouse interferon alpha/beta.

[Renal vein thrombosis in the newborn infant]

In a child born with traumatism to a diabetic mother, an acute thrombosis of the left renal vein occurred. An arteriography performed at the acute stage, established the diagnosis. The newborn received urokinase and heparin administered through an arterial catheterism. An arteriography, repeated at the 3rd day, showed an improvement in the vascularization of the kidney, which returned to normal functions. The radiological symptons of renal vein thrombosis are reviewed including the arteriography which is never used for the diagnosis in newborns. The interest of the use of urokinase and its efficiency in this disorder are discussed. This therapy harmless and efficient seems of interest. Such a therapy has to be tried because of the failure of isolated heparin-therapy and of the sequellae which may be observed after spontaneous recovery or after anticoagulant treatment.

Induction of CD23, CD25 and CD4 expression on an eosinophilic cell line (EoL-3) by interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-5 (IL-5)

The effects of IL-3, GM-CSF and IL-5 on the expression of CD23 (Fc epsilon RII), CD25 (IL-2R/p55) and CD4 on an eosinophilic cell line (EoL-3) were investigated by flow cytometry. A separate incubation with IL-3, GM-CSF or IL-5 alone, did not induce the expression of CD23, CD25, or CD4. However, a sequential incubation with IL-3 for 6 days, then with IL-3 and GM-CSF for the following 6 days, induced a significant expression of CD23 and CD25. After a further incubation for 6 days with IL-3, GM-CSF and IL-5, CD4 was then expressed, while CD23 and CD25 expression still increased. The kinetics of expression of CR3/CD11b were parallel to that of CD23, but the expression of the transferrin receptor (CD71) remained negative. Northern blot analysis revealed the presence of mRNA encoding CD23, CD25 and CD4 in EoL-3 stimulated by IL-3, GM-CSF and IL-5. Culture with GM-CSF induced the binding of radiolabeled IL-5 to EoL-3 cells, with an increased affinity after incubation with IL-3, GM-CSF and IL-5. These data indicate that IL-3, GM-CSF and IL-5, might be involved in the expression of functional markers on eosinophil membrane.

Contributions of leukemia inhibitory factor receptor and oncostatin M receptor to signal transduction in heterodimeric complexes with glycoprotein 130

Leukemia inhibitory factor (LIF), cardiotrophin-1, ciliary neurotrophic factor, and oncostatin M (OSM) lead to heterodimerization of LIF receptor (LIFR) or the OSM-specific receptor (OSMR) with glycoprotein (gp) 130, the common receptor subunit for IL-6-type cytokines. Thereby intracellular signaling via Janus kinases (Jaks) and STAT transcription factors is initiated. We investigated the contributions of LIFR and OSMR to signal transduction in the context of heterodimers with gp130. Chimeric receptors based on the extracellular parts of the IL-5R alpha- and beta-chains were generated, allowing the induced heterodimerization of two different cytoplasmic tails. Our studies demonstrate that upon heterodimerization with the gp130 cytoplasmic region, the cytoplasmic parts of both LIFR and OSMR were critical for activation of an acute phase protein promoter in HepG2 hepatoma cells. The membrane-proximal region of LIFR or OSMR was crucial for the ability of such receptor complexes to induce DNA binding of STAT1 and STAT3 in COS-7 cells. Membrane-distal regions of LIFR and OSMR contributed to STAT activation even in the absence of gp130 STAT recruitment sites. We further show that the Janus kinases Jak1 and Jak2 constitutively associated with receptor constructs containing the cytoplasmic part of LIFR, OSMR, or gp130, respectively. Homodimers of the LIFR or OSMR cytoplasmic regions did not elicit responses in COS-7 cells but did in HepG2 cells and in MCF-7 breast carcinoma cells. Thus, in spite of extensive functional similarities, differential signaling abilities of gp130, LIFR, and OSMR may become evident in a cell-type-specific manner.

Relationship between structure and biochemical phenotype of lecithin:cholesterol acyltransferase (LCAT) mutants causing fish-eye disease

In order to test the hypothesis that fish-eye disease (FED) is due to a deficient activation of lecithin:cholesterol acyltransferase (LCAT) by its co-factor apolipoprotein (apo) A-I, we overexpressed the natural mutants T123I, N131D, N391S, and other engineered mutants in Cos-1 cells. Esterase activity was measured on a monomeric phospholipid enelogue, phospholipase A(2) activity was measured on reconstituted high density lipoprotein (HDL), and acyltransferase activity was measured both on rHDL and on low density lipoprotein (LDL). The natural FED mutants have decreased phospholipase A(2) activity on rHDL, which accounts for the decreased acyltransferase activity previously reported. All mutants engineered at positions 131 and 391 had decreased esterase activity on a monomeric substrate and decreased acyltransferase activity on LDL. In contrast, mutations at position 123 preserved these activities and specifically decreased phospholipase A(2) and acyltransferase activites on rHDL. Mutations of hydrophilic residues in amphipathic helices alpha 3;-4 and alpha His to an alanine did not affect the mutants' activity on rHDL. Based upon the 3D model built for human LCAT, we designed a new mutant F382A, which had a biochemical phenotype similar to the natural T123I FED mutant. These data suggest that residues T123 and F382, located N-terminal of helices alpha 3-4 and alpha His, contribute specifically to the interaction of LCAT with HDL and possibly with its co-factor apoA-I. Residues N131 and N391 seem critical for the optimal orientation of the two amphipathic helices necessary for the recognition of a lipoprotein substrate by the enzyme.

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.

Binding of human tumor necrosis factor to high affinity receptors on HeLa and lymphoblastoid cells sensitive to growth inhibition

Purified human tumor necrosis factor (TNF) was iodinated to high specific activity with good retention of its biological activity, as determined by the cytotoxic titer on murine L929 cells. The binding of 125I-TNF to L929 and human HeLa S2 cells grown in monolayer was initially measured, but high levels of nonspecific binding were observed. Specific binding to high affinity receptors of HeLa S2 cells grown in suspension culture was demonstrated by competitive displacement experiments and analysis of the binding data with the LIGAND program. A KD of 2 X 10(-10) M and 6000 receptors/cell were calculated in this way. These observations provide the first direct evidence for a cellular receptor for TNF. The cell-bound 125I-TNF was internalized at 37 degrees C, presumably by receptor-mediated endocytosis, and subsequently degraded to acid-soluble products. Three lines of human lymphoblastoid cells were examined for sensitivity to the cytostatic effect of TNF and for the presence of high affinity receptors. Daudi and Raji cells were insensitive to TNF and showed very few specific binding sites when incubated with 125I-TNF. Jurkat cells were growth-inhibited by TNF and showed a significantly greater number of specific binding sites than the other lymphoblastoid cells. These findings suggest that the sensitivity of some cell lines to the biological effects of TNF may be correlated with the presence of a relatively high number of receptors for this factor.