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Biomedical subjects

H Engelmann

Publications and source records attributed to H Engelmann.

At least 19 recordsLinked to original sources
PubMed1992

Selective decrease in cell surface expression and mRNA level of the 55-kDa tumor necrosis factor receptor during differentiation of HL-60 cells into macrophage-like but not granulocyte-like cells.

Expression of the two known receptors for TNF was studied in the promyelocytic leukemia cell line HL-60 before and after differentiation of the cells along the granulocyte lineage (induced by incubation with retinoic acid), or along the macrophage lineage (induced by incubation with the phorbol diester, PMA). The extent of inhibition of TNF binding by receptor-specific antisera, as well as the size of the complexes formed after cross-linking TNF to its receptors on intact cells, indicated that both receptor species were expressed on the surface of the undifferentiated HL60 cells. Differentiation into granulocyte-like cells resulted in some increase in TNF binding. The increase was apparently due to enhanced expression of the 75-kDa TNF-R, whereas the amounts of the 55-kDa TNF-R did not change significantly. In contrast, in HL-60 cells induced to differentiate into macrophage-like cells, expression of the 55-kDa TNF-R species was completely abolished. The pattern of TNF-R expression in the differentiated HL-60 cells was similar to that observed in leukocytes isolated from peripheral blood: on granulocytes, there were about equal amounts of both receptor species, whereas on monocytes the 75-kDa receptor was predominant. The loss of 55-kDa receptors during differentiation of HL-60 cells into macrophage-like cells was accompanied by a pronounced decrease in the level of the mRNA for that receptor, suggesting that at least part of the change in TNF-R expression is due to mechanisms that control the amounts of receptor mRNA. Although little is yet known regarding the functional differences between the two receptor species, marked changes in the pattern of their expression, as observed during HL-60 cell differentiation, are likely to alter the kind of response of the cells to TNF and may therefore play an important role in the coordination of TNF effects in the organism.

Cell Differentiation↗
PubMed1992

Stabilization of the bioactivity of tumor necrosis factor by its soluble receptors.

The receptors for tumor necrosis factor (TNF) exist in cell-associated as well as soluble forms, both binding specifically to TNF. Since the soluble forms of TNF receptors (sTNF-Rs) can compete with the cell-associated TNF receptors for TNF, it was suggested that they function as inhibitors of TNF activity; at high concentrations, the sTNF-Rs indeed inhibit TNF effects. However, we report here that in the presence of low concentrations of the sTNF-Rs, effects of TNF whose induction depend on prolonged treatment with this cytokine are augmented, reflecting an attenuation by the sTNF-Rs of spontaneous TNF activity decay. Evidence that this stabilization of TNF activity by the sTNF-Rs follows from stabilization of TNF structure within the complexes that TNF forms with the sTNF-Rs is presented here, suggesting that the sTNF-Rs can affect TNF activity not only by interfering with its binding to cells but also by stabilizing its structure and preserving its activity, thus augmenting some of its effects.

Cell Count↗
PubMed1992

Increased levels of soluble tumor necrosis factor receptors in the sera and synovial fluid of patients with rheumatic diseases.

OBJECTIVE: Recently, 2 classes of cytokine inhibitors have been defined at the molecular level. The largest group comprises the extracellular domains of cell surface cytokine receptors, and includes both tumor necrosis factor receptors (TNF-R). The present study was conducted to investigate the role of TNF inhibitors in arthritis. METHODS: We measured p55 and p75 soluble TNF-R (sTNF-R) in serum and synovial fluid (SF) samples from patients with rheumatic diseases and compared their levels with levels of soluble interleukin-2 receptors (sIL-2R). Sensitive enzyme-linked immunosorbent assays (ELISA), specific for p55 and p75 sTNF-R and for sIL-2R, were used. RESULTS: Serum levels of p75 sTNF-R were 3-4-fold higher than levels of p55 sTNF-R, and both were significantly elevated in patients with osteoarthritis (OA) and rheumatoid arthritis (RA) compared with healthy controls. RA SF levels of sTNF-R were 4-5-fold higher than levels in serum, suggesting local production in the joint, and were significantly higher than levels in the SF of patients with seronegative arthropathy or OA. Furthermore, levels of p55 and p75 sTNF-R, but not sIL-2R or TNF alpha measured by ELISA, were increased in the SF of patients with clinically active RA. The soluble TNF-R in RA and OA SF were functional since they inhibited TNF activity in a cytotoxicity assay in proportion to the levels of inhibitor present. Evaluation of serially obtained serum samples suggested that sTNF-R may be a useful parameter for monitoring RA disease activity. CONCLUSION: Biologically active soluble TNF-R are up-regulated in patients with rheumatic disease and are produced locally in the joints. Measurement of serum levels of TNF-R may be useful for monitoring of disease, and determination of SF levels could be of diagnostic value.

Adult↗
PubMed1992

Cytoplasmic truncation of the p55 tumour necrosis factor (TNF) receptor abolishes signalling, but not induced shedding of the receptor.

The mechanistic relationship between the signalling for the TNF effects by the human p55 TNF receptor (hu-p55-TNF-R) and the formation of a soluble form of the receptor, which is inhibitory to these effects, was explored by examining the function of C-terminally truncated mutants of the receptor, expressed in rodent cells. The 'wild-type' receptor signalled for a cytocidal effect when cross-linked with specific antibodies and exhibited spontaneous shedding. Shedding of the receptor was not affected by TNF but was markedly enhanced by 4 beta-phorbol-12-myristate-13-acetate (PMA). Receptor mutants with 53%, 83% and 96% C-terminal deletions could not signal for the cytocidal effect. Furthermore, they were found to associate with the endogenous rodent receptors, interfering with their signalling. Yet even the deletion of 96% of the intracellular domain did not abolish shedding of the receptor in response to PMA. These findings suggest that signalling and shedding of the p55 TNF-R are mechanistically distinct.

3T3 Cells↗
PubMed1992

Induction of soluble tumour necrosis factor receptors during treatment with interleukin-2.

Interleukin-2 (IL-2) treatment induces other cytokines such as tumour necrosis factor (TNF) TNF may mediate some of the anti-tumour activity of IL-2, but conversely, may contribute to its dose limiting toxicities. Cleaved extracellular domains of the p55 and the p75 TNF receptors (sTNF-R1 and R2) bind to and inhibit the biological activity of TNF in vitro, but may also act as carrier molecules. We have assayed TNF and sTNFR-1 and 2 in the plasma of advanced cancer patients, before and during treatment with IL-2. Plasma levels of TNF in 22 patients were not significantly different from 25 normal controls, but levels of sTNFR-1 and sTNFR-2 were higher (P < 0.001). Levels of TNF and both its soluble receptors were significantly increased in 13 patients receiving IL-2 therapy. Maximum induced levels of sTNFR-1 and sTNFR-2 correlated closely with maximum induced levels of TNF (P < 0.001), but peak levels of sTNFR-1 and two were achieved 24-48 h after peak TNF. Levels of TNF and sTNF-Rs did not correlate with toxicity. Treatment with IL-2 leads not only to induction of TNF but also soluble binding proteins at levels which may modulate its biological activity.

Breast Neoplasms↗
PubMed1992

Elevated serum levels of soluble tumour necrosis factor receptors (sTNF-R) in patients with HIV infection.

Serum levels of the soluble form of tumour necrosis factor receptor type II (p75) (sTNF-R) were determined in HIV-infected individuals and risk groups and were then correlated with the course of infection and prognosis. sTNF-R levels were determined by an ELISA with MoAbs and polyclonal antibodies to urine-derived sTNF-R proteins. The mean +/- s.e. levels of sTNF-R in the sera of 49 HIV+ male homosexuals, 34 HIV- male homosexuals and 44 matched controls were 6.1 +/- 0.3 ng/ml, 4.4 +/- 0.3 ng/ml and 3.4 +/- 0.2 ng/ml, respectively. All these values were significantly different between each of the groups (P less than 0.001-0.05). Sequential studies of sTNF-R revealed higher levels following seroconversion in 5/8 individuals, remained persistently high during the asymptomatic phase of the infection and became even more elevated in some ARC and AIDS patients. At the same time TNF-alpha was undetectable in sera obtained from HIV+ male homosexuals and from healthy controls. This was independent of stage of HIV infection, serum sTNF-R level and type of ELISA kit used. These findings suggest that TNF-alpha/TNF-R system is turned on before and during HIV infection and raise the possibility that sTNF-R, the natural inhibitor of TNF, may be of importance in determining the course and probably prognosis of the disease.

Enzyme-Linked Immunosorbent Assay↗
PubMed1992

Variation in serum levels of the soluble TNF receptors among healthy individuals.

Soluble forms of the two receptors for tumor necrosis factor (TNF) are present in human sera at concentrations that increase greatly in various disease states as well as varying among healthy individuals. Measurements of the soluble TNF receptor (sTNF-R) concentrations in healthy individuals at time lapses of 3 months (17 individuals) or 1 year (51 individuals) showed a significant correlation between the first and the second measurements from each individual, implying that individual differences are stable. Since the sTNF-Rs are believed to function as physiological attenuators of TNF activity, these steady individual differences may contribute to differences in the severity of the harmful effects of TNF in disease states.

Enzyme-Linked Immunosorbent Assay↗
PubMed1991

Human neutrophil elastase releases a ligand-binding fragment from the 75-kDa tumor necrosis factor (TNF) receptor. Comparison with the proteolytic activity responsible for shedding of TNF receptors from stimulated neutrophils.

To localize the protease(s) involved in shedding of tumor necrosis factor receptors (TNF-R) from activated neutrophils (PMN) (Porteu, F., and C. Nathan (1990) J. Exp. Med. 172, 599-607), we tested subcellular fractions from PMN for their ability to cause loss of TNF-R from intact cells. Exposure of PMN to sonicated azurophil granules at 37 degrees C resulted in inhibition of 125I-TNF binding; 50% inhibition ensued when PMN were treated for approximately 1 min with azurophil granules equivalent to 2-3 PMN per indicator cell. The TNF-R-degrading activity in azurophil granules were identified as elastase by its sensitivity to diisopropyl fluorophosphate (DFP), alpha 1-antitrypsin and N-methoxysuccinyl-Ala-Ala-Pro-Val chloromethyl ketone (MSAAPV-CK), and by the ability of purified elastase to reproduce the effect of azurophil granules. Elastase preferentially acted on the 75-kDa TNF-R, reducing by 85-96% the binding of 125I-TNF to mononuclear cells expressing predominantly this receptor, while having no effect on endothelial cells expressing almost exclusively the 55-kDa TNF-R. Elastase-treated PMN released a 32-kDa soluble fragment of p75 TNF-R that bound TNF and reacted with anti-TNF-R monoclonal antibodies. In contrast, fMet-Leu-Phe-activated PMN shed a 42-kDa fragment from p75 TNF-R, along with similar amounts of a 28-kDa fragment from p55 TNF-R. Shedding of both TNF-Rs by intact activated PMN was more extensive than shedding caused by elastase and was completely resistant to DFP and MSAAPV-CK. Thus, the TNF-R-releasing activity of azurophil granules is distinct from that operative in intact stimulated PMN and could provide an additional mechanism for the control of cellular responses to TNF at sites of inflammation.

Adult↗
PubMed1991

The gene for the type II (p75) tumor necrosis factor receptor (TNF-RII) is localized on band 1p36.2-p36.3.

The gene encoding the type II (p75) tumor necrosis factor receptor (TNF-RII) has been localized on human chromosome 1, band 1p36.2 by nonradioactive in situ hybridization. The gene encoding the type I (p55) TNF-R, which is structurally homologous to the type II (p75) TNF-R, has been previously localized on chromosome 12 band 12p13. Thus, despite their probable common ancestry, the genes for the two TNF-Rs are localized on different chromosomes.

Base Sequence↗
PubMed1991

Monoclonal antibodies to the soluble human IL-6 receptor: affinity purification, ELISA, and inhibition of ligand binding.

Soluble IL-6 receptor (IL-6-R) purified to homogeneity from normal human urine was used for immunization of mice and rabbits. Spleen cells derived from a mouse showing a high binding titer to IL-6-R in an inverted solid phase radioimmunoassay (IsRIA) and in a Western blotting analysis were fused to mouse myeloma cells. The hybridomas were screened by the IsRIA, and 30 positive clones were isolated and characterized. They were suitable for affinity purification of the IL-6-R and for its detection by Western blot analysis, by ELISA and by sandwich type sRIA. Most of them inhibited the binding of labeled IL-6-R to IL-6 in a solid phase RIA.

Animals↗
PubMed1991

Soluble and cell surface receptors for tumor necrosis factor.

Tumor necrosis factor (TNF) initiates its multiple effects on cell function by binding at a high affinity to specific cell surface receptors. Two different molecular species of these receptors, which are expressed differentially in different cells, have been identified. The cDNAs of both receptors have recently been cloned. Antibodies to one of these receptor species (the p55, type I receptor) can trigger a variety of TNF like effects by cross-linking of the receptor molecules. Thus, it is not TNF itself but its receptors that provide the signal for the response to this cytokine. The intracellular domains of the two receptors differ in structure, suggesting that they mediate different activities. Their extracellular domains, however, are structurally related. Both contain cysteine-rich repeats which are homologous to repeated structures found in the extracellular domains of the nerve growth factor receptor and the CDw40 protein. Truncated soluble forms of the two receptors, corresponding to these cysteine-rich repeated structures, have been detected in human urine and were later found to be present also in the serum. The serum levels of those soluble TNF receptors increase dramatically in certain pathological situations. Release of the soluble receptors from the cells seems to occur by proteolytic cleavage of the cell surface forms and appears to be a way of down-regulating the cell response to TNF. Because of their ability to bind TNF, the soluble receptors exert an inhibitory effect on TNF function, and may thus act as physiological attenuators of its activity.

Animals↗
PubMed1990

Antibodies to a soluble form of a tumor necrosis factor (TNF) receptor have TNF-like activity.

Immunological cross-reactivity between tumor necrosis factor (TNF) binding proteins which are present in human urine (designated TBPI and TBPII) and two molecular species of the cell surface receptors for TNF is demonstrated. The two TNF receptors are shown to be immunologically distinct, to differ in molecular weight (58,000 and 73,000), and to be expressed differentially in different cells. It is further shown that polyclonal antibodies against one of the TNF binding proteins (TBPI) display, by virtue of their ability to bind the TNF receptor, activities which are very similar to those of TNF. These antibodies are cytotoxic to cells which are sensitive to TNF toxicity, induce resistance to TNF toxicity, enhance the incorporation of thymidine into normal fibroblasts, inhibit the growth of chlamydiae, and induce the synthesis of prostaglandin E2. Monovalent F(ab) fragments of the polyclonal antibodies lack TNF-like activities, but acquire them upon cross-linking with anti-F(ab)2 antibodies, suggesting that the ability of the anti-TBPI antibodies to mimic TNF correlates with their ability to cross-link the TNF receptors. This notion was further supported by data obtained in a comparative study of the TNF-like cytotoxicity of a panel of monoclonal antibodies against TBPI. The induction of TNF-like effects by antibodies to a TNF receptor suggests that TNF is not directly involved in intracellular signalling. Rather, it is the receptors to this cytokine which, when properly triggered in a process which appears to involve clustering of these receptors, transduce the signal for response to TNF into the cell's interior.

Animals↗
PubMed1990

Purification of soluble cytokine receptors from normal human urine by ligand-affinity and immunoaffinity chromatography.

Affinity chromatography of crude human urinary proteins on either human recombinant interleukin-6 (rIL-6) or human recombinant interferon-gamma (rIFN-gamma) or anti IFN-gamma receptor (IFN-gamma-R) monoclonal antibodies (McAb) yielded the two respective soluble receptors in significant amounts. A single sequence of 30 amino acid residues was obtained by N-terminal microsequencing of the protein peak purified in tandem by affinity chromatography on an IL-6 column and reversed-phase high-performance liquid chromatography. This sequence was identical with the predicted N-terminal sequence of IL-6-R as previously reported. The purified IL-6-R retained its biological activity. It was used for the preparation of specific anti IL-6-R monoclonal antibodies. Analysis of the eluted proteins from both IFN-gamma and anti IFN-gamma-R columns by inhibition of solid-phase radioimmunoassay, enzyme-linked immunosorbent assay, sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blotting proved the existence of soluble IFN-gamma-R in normal urine. This finding together with the already known presence of soluble TNF receptors and a soluble IL-2 receptor found both in plasma and in urine indicates that release of soluble cytokine receptors into body fluids is a general phenomenon which occurs under normal physiological conditions.

Chromatography, Affinity↗
PubMed1990

Two tumor necrosis factor-binding proteins purified from human urine. Evidence for immunological cross-reactivity with cell surface tumor necrosis factor receptors.

Two proteins which specifically bind tumor necrosis factor (TNF) were isolated from human urine by ligand (TNF)-affinity purification, followed by reversed phase high performance liquid chromatography. The molecular weights of the two proteins, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, were similar (about 30,000). Both proteins provided protection against the cytocidal effect of TNF in vitro and both bound TNF-alpha more effectively than TNF-beta. Antibodies raised against each of the proteins had an inhibitory effect on the binding of TNF to cells, suggesting that both proteins are structurally related to the TNF receptors. However, the two proteins differed in NH2-terminal amino acid sequences: Asp-Ser-Val-Cys-Pro- in one and Val-Ala-Phe-Thr-Pro- in the other. The NH2-terminal sequence of the former protein was invariable, while that of the latter was truncated to varying degrees. The two proteins were also immunologically distinct. The relative efficacy of anti-sera against the two proteins in inhibiting the binding of TNF to cells varied markedly from one line of cells to another. Evidence has been presented recently for the existence of two distinct molecular species of cell surface receptors for TNF and for differential expression of those two receptors by cells of different lines. The findings presented in this study are consistent with the notion that the urinary TNF-binding proteins constitute soluble forms of the two molecular species of the cell surface TNF receptors.

Binding, Competitive↗
PubMed1990

[The attaching of bypass cannulas to the duodenum of dairy cows].

Described in this paper is a bypass cannula for the small intestine (duodenum, ileum) of dairy cows, with reference being also made to the surgical method used on the duodenum. The bypass cannula is made up to flexible, curved single cannulas, 25 mm in diameter, which by a new design are safely connected to each other in a jointless, non-angular manner. The cannulas are manufactured of Type B 400/40 K PVC paste by means of a casting technique. The connecting link consists of a PVC or piacryl tube, about 45 mm in length, which is pressed by means of sleeve nuts against the collars of the two cannula openings. The bypass cannula weights 160 g and is tightly attached to the body of the animal, so that neither grazing nor calving are obstructed. Bypass problems of the past (leakage from proximal cannula, clogging, accidental opening of cannula connection) have not even occurred to high-performance cows with feed uptake rates between 3.0 and 3.5 kg of dry matter to 100 kg of live weight and corresponding digestion passages up to 400 l daily.

Animals↗
PubMed1989

Soluble cytokine receptors are present in normal human urine.

Affinity chromatography of crude human urinary proteins on either human rIL-6, human rIFN-gamma, or anti-IFN-gamma-R mAb yielded the two respective soluble receptors in significant quantities. A single sequence of 30 amino acid residues was obtained by NH2-terminal microsequencing of the protein peak purified in tandem by affinity chromatography on an IL-6 column and reversed-phase HPLC. This sequence was identical to the predicted NH2-terminal sequence of IL-6-R as previously reported. Analysis of the eluted proteins from both IFN-gamma and anti-IFN-gamma-R columns by inhibition of solid phase RIA, ELISA, SDS-PAGE, and Western blotting proved the existence of soluble IFN-gamma-R in normal urine. Our finding, together with the already known presence of urinary TNF binding proteins and a soluble IL-2-R both in plasma and in urine, indicates that release of soluble cytokine receptors into body fluids is a general phenomenon that occurs under normal physiological conditions.

Amino Acid Sequence↗
PubMed1989

A tumor necrosis factor-binding protein purified to homogeneity from human urine protects cells from tumor necrosis factor toxicity.

Unfractionated preparations of the proteins of human urine provided protection against the in vitro cytocidal effect of tumor necrosis factor (TNF). In certain cells, the proteins decreased expression of the receptors for TNF in a temperature-dependent way. In all cells examined, the proteins were found to interfere also with the binding of both TNF and interleukin-1 when applied directly into the binding assays. That effect could be observed in the cold, suggesting that it was independent of cellular metabolism. A protein which protects cells against the cytotoxicity of TNF was purified from human urine by chromatography on CM-Sepharose followed by high performance liquid chromatography on Mono Q and Mono S columns and reversed phase high performance liquid chromatography. This protein is a very minor constituent of normal urine, with an apparent molecular weight of about 27,000 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis under both reducing and nonreducing conditions. Homogeneity of the purified protein was confirmed by microsequence analysis which revealed a single N-terminal sequence: Asp-Ser-Val-Cys-Pro-. The protein protected cells from TNF toxicity at concentrations of a few nanograms per ml and interfered with the binding of both TNF-alpha and TNF-beta to cells, when applied simultaneously with the cytokines. However, unlike crude preparations of the urinary proteins, the purified protein did not induce in cells a decrease in ability to bind TNF nor did it interfere with the binding of interleukin-1 to its receptor. Direct, specific binding to the protein of TNF-alpha and, to a lesser extent, also TNF-beta, but not of interleukin-1 nor interferon-gamma could be demonstrated. It is suggested that this protein blocks the function of TNF by competing for TNF with the TNF receptor and not by interacting with the target cell.

Binding, Competitive↗