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T Espevik

Publications and source records attributed to T Espevik.

At least 91 records · Page 5Linked to original sources
PubMed1993

The involvement of CD14 in stimulation of cytokine production by uronic acid polymers.

In this study the molecular mechanisms behind the stimulatory activities of the uronic acid polymers poly mannuronic acid (poly M), high M alginate and oxidized cellulose (C60XY) were investigated and compared with lipopolysaccharide (LPS). The cytokine-inducing abilities of the uronic acid polymers and LPS were examined on CD14-positive human monocytes and CD14-negative U373 astrocytoma cells. It was found that LPS induced monocytes and U373 cells to produce tumor necrosis factor (TNF) and interleukin(IL)-6, respectively, by different mechanisms. The poly uronic acids induced monocytes to produce TNF, but with 100-1000 times less potency compared to LPS. On U373 cells, LPS at concentrations > or = 32 ng/ml resulted in a dose-related IL-6 production, whereas the poly uronic acids had negligible effects even at 1 mg/ml. The binding data demonstrate that only the CD14-positive monocytes in the peripheral blood mononuclear cells population bound poly M. Furthermore, poly M was found to bind to CD14 in the presence of serum. Antibodies against CD14 also inhibited the TNF-inducing activity of the three uronic acid polymers tested. In conclusion, these results demonstrate that uronic acid polymers induce TNF production through mechanisms which involve CD14.

Alginates↗
PubMed1993

Gene expression and secretion of cytokines and cytokine receptors from highly purified CD56+ natural killer cells stimulated with interleukin-2, interleukin-7 and interleukin-12.

Interleukin (IL)-2 IL-7 and IL-12 stimulate the generation of lymphokine-activated killer activity and proliferation in natural killer (NK) cells by different mechanisms. In this study, we have compared the ability of IL-2, IL-7 and IL-12 to induce expression of cytokines and cytokine receptors both at the gene and protein level. IL-2 and IL-12 stimulated the CD56+ NK cells to release significant amounts of soluble p55 and p75 tumor necrosis factor receptor (TNFR), whereas less amounts of soluble TNFR were detected in IL-7-stimulated cultures. The p55 and p75 TNFR mRNA were expressed in resting NK cells, and no further induction was observed after cytokine-stimulation. Compared to the effects of IL-2, IL-7 induced lower, but substantial levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA, and IL-7 was a more potent GM-CSF-inducing stimulus than IL-12. IL-12 induced higher levels of interferon-gamma (IFN-gamma) mRNA than did IL-2, and IL-7 only weakly influenced the IFN-gamma expression. In accordance with the mRNA studies, IL-7 induced the secretion of high amounts of GM-CSF and no or low levels of IFN-gamma, whereas high amounts of IFN-gamma and low levels of GM-CSF were detected in supernatants from IL-12-stimulated NK cells. In conclusion, IL-2, IL-7 and IL-12 differentially regulate expression of cytokines and cytokine receptors both at the gene and protein level.

Animals↗
PubMed1993

Multiple derangements of cytokine homeostasis in mice infected with immunosuppressive retrovirus.

Altered production of various lymphokines is considered an important factor in retrovirus-induced immunosuppression. We have measured the production of interleukin 2 (IL-2), interleukin 6 (IL-6), transforming growth factor beta 1 (TGF-beta 1), and tumor necrosis factor alpha (TNF-alpha) in splenocytes of retrovirus-infected NMRI mice. In Con A-stimulated splenocytes from mice infected with the acute transforming retrovirus Friend leukemia complex (FLC), TNF-alpha and IL-6 production was significantly suppressed. We compared cytokine production in infection with Friend-derived murine immunosuppressive virus (Fd-MIV), a low oncogenic retrovirus that induces a immunosuppression of a magnitude similar to that of FLC. In Fd-MIV infection, the ability of lymphoid cells to produce both IL-2 and TNF-alpha was suppressed. The suppression of these cytokines coincided with the suppression of the primary antibody response. In contrast to FLC infection, the production of IL-6 was elevated. Furthermore, increased production of TGF-beta was found in unstimulated splenocytes from Fd-MIV-infected mice. Infection with immunosuppressive retroviruses induces a complex derangement of T-cell cytokine homeostasis and the relative contributions of the various factors to the immunosuppressed state are difficult to assess at present.

Animals↗
PubMed1993

Synergistic effects of interleukin 4 and interleukin 12 on NK cell proliferation.

Our previous studies have demonstrated that interleukin12 (IL-12) (cytotoxic lymphocyte maturation factor/NK cell stimulatory factor) and IL-7 alone have the ability to generate high LAK activity and low proliferative activity in CD56+ NK cells. This study was undertaken to examine the influence of IL-4 on the IL-12-induced activation of CD56+ NK cells. IL-4 did not affect the IL-12-induced generation of LAK activity in CD56+ cells, in contrast to an inhibition of IL-2 and IL-7-induced LAK activity. Most interestingly, the combination of IL-4 and IL-12 resulted in a synergistic proliferative activity (8-fold) in the CD56+ NK cells, and a marked increase in the cell yield at day 5 was detected. Furthermore, the potent effect of IL-4 on IL-12-induced proliferation was restricted to the CD56+ NK cells, as CD56- cell populations were found unresponsive to the combination of IL-4 and IL-12. Furthermore, IL-4 induced a slight increase in the IL-12-stimulated TNF production. IL-12 enhanced the IL-12 receptor (R) expression and IL-4R expression in the CD56+ NK cells. Combined treatment with IL-12 and IL-4 further enhanced the IL-12R expression, most prominently in the CD56+, CD16- NK subpopulation. The increased IL-4R expression induced by IL-12 and the increased IL-12R expression induced by IL-4 may explain the synergistic proliferative activity detected in response to IL-12 and IL-4. IL-4 seems to possess unique stimulatory properties towards resting CD56+ NK cells, when used as a costimulus with IL-12.

Antigens, CD↗
PubMed1993

High concentrations of the soluble p55 tumour necrosis factor receptor in human seminal plasma.

Soluble TNFRs (tumour necrosis factor receptors) inhibit in-vivo and in-vitro bioactivities of TNF, and thus the secretion of soluble TNFRs could be a physiological principle to attenuate the bioactivities of TNF. Two types of TNFR have been identified and both forms can be released from cells. In this study, soluble TNFRs in seminal plasma from three groups of men were analysed: from men with normal semen quality (n = 32), with reduced semen quality (n = 7) and vasectomized men (n = 3). Sensitive and specific enzyme-linked immunosorbent assays were utilized to detect soluble TNFRs in seminal plasma, based on capture antibodies directed against non-TNF-binding sites of the TNFRs and digoxigenin (DIG)-labelled TNF. The mean +/- standard deviation levels of p55 TNFR were 56.4 +/- 20, 64.4 +/- 17 and 45.4 +/- 5 ng/ml in the three groups, respectively. The concentration of p75 TNFR was < 1 ng/ml in all groups. The results suggest an exclusive existence of high amounts of the soluble p55 TNFR in seminal plasma. Seminal plasma from vasectomized men contained p55 TNFR at approximately the same levels as the specimen from the two other groups, indicating that the source of p55 TNFR is not the testis but rather some tissue more distal in the male genital tract, such as the prostate or the seminal vesicles. The soluble p55 TNFR was purified from human seminal plasma, using affinity and gel filtration chromatography. Further characterization of the purified p55 revealed a protein with a molecular weight of approximately 22 kDa, both under reducing and non-reducing conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, Affinity↗
PubMed1993

Similar mechanisms of action of defined polysaccharides and lipopolysaccharides: characterization of binding and tumor necrosis factor alpha induction.

Little has been reported about the effects of different polysaccharides on cytokine production from human monocytes. In this study, we show that several well-defined polysaccharides, including polymers with different sizes of beta 1-4-linked D-mannuronic acid (poly-M, high-M alginate, and M-blocks) and cellulose oxidized in the C-6 position, induced human monocytes to produce tumor necrosis factor alpha (TNF-alpha). Poly-M was the most efficient polysaccharide tested and, on a weight basis, was approximately as efficient as lipopolysaccharide (LPS) from Escherichia coli. TNF-alpha production was shown to depend strongly on the molecular weights of poly-M and high-M alginate, with maximal TNF-alpha production occurring at molecular weights above 50,000 and 200,000, respectively. G-blocks, alpha 1-4-linked L-guluronic acid polymers that did not induce cytokine production from monocytes, reduced the cytokine production induced by the beta 1-4-linked polyuronic acids and LPS. Furthermore, both G-blocks and LPS were found to inhibit the binding of poly-M to monocytes, as measured by flow cytometry. In addition, we found that the binding of LPS to monocytes was inhibited by G-blocks, M-blocks, and poly-M. Our results indicate that beta 1-4-linked polyuronic acids and LPS may stimulate monocytes to produce TNF-alpha by similar mechanisms and may bind to a common receptor.

Biological Assay↗
PubMed1993

Increased levels of soluble tumor necrosis factor-alpha receptors in serum from pregnant women and in serum and urine samples from newborns.

Secretion of soluble cytokine receptors has been suggested as a mechanism of regulating cytokine activity in vivo. In this study, the presence of soluble receptors for tumor necrosis factor-alpha (TNF-alpha) in serum samples from pregnant women and newborn babies was examined by using TNF-alpha receptor-specific immunoassays. Serum from pregnant women contained the 55-kD TNF-alpha receptor p55 [6.4 micrograms/L, interquartile range, i.e. the difference between the 25th and 75th percentile, (IQR) 7.2 micrograms/L], whereas p55 was not detected in control sera from nonpregnant, fertile women. The levels of p55 were also elevated in serum from newborns (3.2 micrograms/L, IQR 0.7 micrograms/L). Furthermore, first-voided urine from newborns contained high levels of p55 (44.6 micrograms/L, IQR 96.6 micrograms/L). The concentration of p55 in the neonatal period was significantly higher than that of children later in childhood (p < 0.05). The concentration of p55 was 7.3 micrograms/L, IQR 13.8 micrograms/L, in urine samples from a group of preschool children (1 mo < age < 5 y) and 6.9 micrograms/L, IQR 2.9 micrograms/L, in urine samples from children in a higher age group (5 y < age < 10 y). The concentration of the 75-kD TNF-alpha receptor in urine did not differ significantly between the different age groups studied. The elevated p55 serum levels of pregnant women and neonates are suggestive of a pregnancy-associated release of soluble receptors. The high concentration of p55 in neonatal urine may reflect a postpartum elimination of soluble receptors shed during pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1993

Soluble receptors for tumor necrosis factor: occurrence in association with normal delivery at term.

OBJECTIVE: To compare levels of tumor necrosis factor (TNF) and interleukin 1 (IL-1) and 6 (IL-6) with levels of the soluble receptors for TNF in maternal and neonatal urine and amniotic fluid (AF). METHODS: Levels of soluble TNF receptors (p55, p75) in AF and urine from 21 women and their newborns were measured by immunoassay. The amniotic concentrations of IL-1 and IL-6 were assessed by biologic assays, whereas an immunoassay was used to measure TNF levels. The comparison between receptor concentrations in different compartments was performed by one-way analysis of variance, and Student t test was used to compare pairs of groups. Correlation studies were performed when indicated. RESULTS: A high correlation was observed between the concentrations of p55 and p75 in all compartments. The concentration of p55 in AF was significantly higher than that in both maternal and neonatal urine, but the correlation between TNF receptor concentrations in the AF samples and the concomitant levels of cytokines was not statistically significant. CONCLUSION: The high concentration of receptors in the AF compared to those of other biologic compartments suggests that the pregnancy-associated increased receptor shedding takes place in intrauterine tissues. Physiologic levels of cytokines, such as those accompanying normal delivery at term, did not seem to influence the soluble TNF receptor release.

Amniotic Fluid↗
PubMed1992

Soluble CD14 participates in the response of cells to lipopolysaccharide.

CD14 is a 55-kD protein found both as a glycosylphosphatidyl inositol-linked protein on the surface of mononuclear phagocytes and as a soluble protein in the blood. CD14 on the cell membrane (mCD14) has been shown to serve as a receptor for complexes of lipopolysaccharide (LPS) with LPS binding protein, but a function for soluble CD14 (sCD14) has not been described. Here we show that sCD14 enables responses to LPS by cells that do not express CD14. We have examined induction of endothelial-leukocyte adhesion molecule 1 expression by human umbilical vein endothelial cells, interleukin 6 secretion by U373 astrocytoma cells, and cytotoxicity of bovine endothelial cells. None of these cell types express mCD14, yet all respond to LPS in a serum-dependent fashion, and all responses are completely blocked by anti-CD14 antibodies. Immunodepletion of sCD14 from serum prevents responses to LPS, and the responses are restored by addition of sCD14. These studies suggest that a surface anchor is not needed for the function of CD14 and further imply that sCD14 must bind to additional proteins on the cell surface to associate with the cell and transduce a signal. They also indicate that sCD14 may have an important role in potentiating responses to LPS in cells lacking mCD14.

Animals↗
PubMed1992

[Secretion of soluble receptors for tumor necrosis factor. An immunologic buffer mechanism during normal pregnancy?].

High concentrations of tumour necrosis factor may threaten the well-being of the foetus. Secretion of soluble cytokine receptors has been suggested as a mechanism for regulating cytokine activity in vivo. In this study pregnancy-related materials were examined for the presence of soluble receptors (p55 and p75) for tumour necrosis factor. In contrast to control materials, serum and urine samples from pregnant women and newborns contained high concentrations of p55, and p55 was highly expressed by villous syncytiotrophoblasts. Thus, the present data suggest that shedding of specific receptors may contribute to the regulation of tumour necrosis factor activity throughout a normal pregnancy.

Cytokines↗
PubMed1992

p55 and p75 tumor necrosis factor receptors in patients with chronic lymphocytic leukemia.

We studied the expression of the two tumor necrosis factor (TNF) receptors, p55 and p75, on B cells from patients with chronic lymphocytic leukemia (CLL), and the presence of soluble TNF receptors in serum. Expression of membrane-associated receptors was quantified by double labeling of peripheral blood mononuclear cells (PBMC) with monoclonal antibodies against CD19 and p55/p75 TNF receptors and flow cytometry. A high fraction of the CD19+ cells expressed the p55 receptor (44% +/- 34% [SD]) and p75 receptor (61% +/- 31%). In healthy controls, 0% to 1% of the CD19+ cells expressed the p55 receptor and 0% to 10% expressed the p75 receptor. Incubation of CD19+ cells with 10 ng/mL of TNF increased the incorporation of thymidine in 11 patients tested, and this was decreased to 65% (P < .05) by antibodies to the p55 receptor or the p75 receptor, and to 35% +/- 7% (P < .001) when both antibodies were combined. With an enzyme-linked immunoassay, we measured soluble TNF receptors in serum from CLL patients. The mean level of p55 receptors was increased to 12.9 +/- 8.9 ng/mL (P < .000001 v normal). The mean level of p75 receptors was increased to 13 +/- 24 ng/mL (P = .01 v normal). The membrane expression of the two receptors was positively correlated (r +/- 97, P < .01); however, there was no correlation between membrane expression and serum concentration of either receptor. Autologous serum containing high levels of soluble TNF receptors inhibited TNF-induced proliferation of CD19+ cells. In conclusion, we have demonstrated that neoplastic cells from patients with CLL have increased expression of p55 and p75 TNF receptors, and that both receptors mediate signal to proliferation. Furthermore, serum from CLL patients has elevated levels of soluble TNF receptors, which may counteract the proliferative effect of TNF.

Antibodies, Monoclonal↗
PubMed1992

A comparative study of IL-12 (cytotoxic lymphocyte maturation factor)-, IL-2-, and IL-7-induced effects on immunomagnetically purified CD56+ NK cells.

IL-12, or cytotoxic lymphocyte maturation factor, is a recently cloned cytokine shown to influence lymphokine-activated killer cells activity in heterogeneous lymphocyte populations, proliferative activity as a costimulus in PBMC/PBL populations and IFN-gamma production in PBL. We have investigated the effects of IL-12 on immunomagnetically highly purified CD56+ lymphocytes, and compared the effects with those of IL-7 and IL-2. Our results show that IL-12 directly generated high lymphokine-activated killer cell activity in CD56+ NK cells, without the need for accessory cells. The IL-12-induced lymphokine-activated killer cell activity reached 50% of what was obtained with IL-2. In contrast, only low proliferative activity was induced by IL-12, as 10% of the IL-2-induced- and approximately 50% of the IL-7-induced proliferative activity was detected with IL-12. The CD56+ cells expressed high levels of IL-2R alpha and 75-kDa TNFR in response to IL-12, comparable to what was registered with IL-2 and IL-7. Furthermore, an extensive up-regulation of the CD56 Ag, to the level obtained with IL-2, was detected in the CD56+ NK cells in the presence of IL-12. Stimulation with IL-7 resulted in a more limited CD56 up-regulation in the CD56+ NK cells. Low concentrations of TNF-alpha were produced in response to both IL-12 and IL-7, with little or no TNF-beta production. Time course of the IL-2-induced TNF production revealed an initial TNF-alpha production, whereas significant levels of TNF-beta were detected after 72 h. The effects of both IL-12 and IL-7 on the CD56+ NK cells were inhibited by an anti-TNF-alpha mAb. Thus, IL-12 can directly influence NK cell activities in purified CD56+ cells, and endogenously produced TNF-alpha is involved in mediating the effects of both IL-12 and IL-7.

Antibodies, Monoclonal↗
PubMed1992

Anti-tumor necrosis factor receptor and tumor necrosis factor agonist activity by an anti-idiotypic antibody.

Tumor necrosis factor (TNF) is a cytokine which, among other properties, is a principle mediator of inflammation and septic shock. It acts upon target cells by binding to specific cell surface receptors. A10G10 is a murine monoclonal antibody which recognizes human TNF and neutralizes its activity. A rabbit polyclonal antibody directed at the antigen-binding site of A10G10 was raised and affinity purified over an A10G10 column. The resultant anti-idiotypic antibody recognized not only A10G10 but also both TNF receptors. It showed TNF agonist activity in two different TNF bioassays, and competed with several anti-TNF receptor monoclonal antibodies and TNF itself for binding to cells. These results represent an example of a method for obtaining antibodies to a ligand-specific receptor in the absence of the receptor itself.

Animals↗
PubMed1992

Effects of n-3 and n-6 fatty acids on tumor necrosis factor cytotoxicity in WEHI fibrosarcoma cells.

Modulation by fatty acids of the cytotoxic effect of recombinant tumor necrosis factor alpha (TNF) toward WEHI 164 mouse fibrosarcoma cells has been examined. Preincubating the highly TNF-sensitive WEHI clone 13 cells for 44 hr with 50 mumol/L of 20:5n-3, 22:6n-3, 18:3n-6, 20:3n-6 or 20:4n-6 reduced cell survival 22 hr after challenge with TNF (40 ng/L) by 65%, 72%, 60%, 98% and 85%, respectively. In comparison, 18:3n-3, 18:2n-6 and 18:1n-9 had only negligible effects on TNF-induced toxicity. Different extent of fatty acid incorporation into cell total phospholipids or triglycerides could not explain the observed effects on TNF cytotoxicity, and the enhanced cytotoxicity could therefore not be explained merely by an increased unsaturation of the cell membranes. In addition to the fatty acid supplied, preincubation with 18:2n-6, 18:3n-6 or 18:3n-3 also enriched the cells with 20:2n-6, 20:3n-6 and 20:3n-3, respectively, most likely due to chain elongation. The results suggest that the WEHI cells have a low delta 6 desaturase activity, and that n-6 and n-3 acids must have at least 3 or 4 double bonds, respectively, to enhance TNF cytotoxicity in WEHI cells. Dexamethasone partly inhibited TNF-induced cytotoxicity, while cyclooxygenase, thromboxane synthetase or lipoxygenase inhibitors had no or negligible effects. The antioxidant butylated hydroxyanisole (BHA) completely inhibited TNF-induced cytotoxicity, while the structurally and functionally similar antioxidant butylated hydroxytoluene had no such effect, indicating that BHA does not block TNF cytotoxicity through its antioxidant effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Soluble TNF receptors in amniotic fluid and in urine from pregnant women.

Secretion of soluble cytokine receptors has been suggested as a mechanism for regulation of cytokine activity in vivo. The present investigation was performed to study whether secretion of soluble TNF (tumor necrosis factor) receptors (TNFRs) might be associated with pregnancy. There are two known molecular species of the TNFR, the 55-kDa TNFR and the 75-kDa TNFR. The 75-kDa, as well as the 55-kDa TNFR, was detected in urine from pregnant women, whereas only the 75-kDa TNFR was detected in urine from the non-pregnant group. The concentration of TNFRs in urine increased towards term and was reduced in association with spontaneous delivery. The soluble forms of both TNFRs were also detected in amniotic fluid. Collectively, the data suggest that secretion of soluble TNFRs during pregnancy might be a defence mechanism for the protection of the fetus against TNF action.

Amniotic Fluid↗
PubMed1992

Butylated hydroxyanisole specifically inhibits tumor necrosis factor-induced cytotoxicity and growth enhancement.

The effect of commonly used food antioxidants on recombinant tumor necrosis factor alpha (rTNF-alpha)-induced cytotoxicity, growth enhancement and adhesion has been evaluated. Butylated hydroxyanisole (BHA) and 4-hydroxymethyl-2,6-di-t-butylphenol (HBP) were the only two of nine antioxidants that completely inhibited rTNF-alpha-induced cytotoxicity in L929 and WEHI 164 fibrosarcoma cells. Ethoxyquin, propyl gallate and butylated hydroquinone only partially inhibited rTNF-alpha-induced cytotoxicity, while the antioxidants butylated hydroxytoluene (BHT), alpha-tocopherol, ascorbic acid and thiodipropionic acid had minimal effects. The only difference between the molecular structure of the efficient HBP and the non-efficient BHT, is a hydroxymethyl group instead of a hydroxyl group on the phenolic ring. Neither BHA nor BHT inhibited the activation of NF kappa B after 10 or 60 min challenge with rTNF-alpha in L929 cells. BHA also inhibited rTNF-alpha-induced, but not rIL-1 beta-induced growth enhancement in FS-4 fibroblasts. Further, BHA blocked both rTNF-alpha-induced and rIL-1 beta-induced prostaglandin E2 synthesis in FS-4 fibroblasts. BHA inhibited the rTNF-alpha-induced release of arachidonic acid in both FS-4 and L929 cells, suggesting that BHA inhibits cellular phospholipase(s). Neither alpha-tocopherol nor BHA inhibited rTNF-alpha-induced adhesiveness of human endothelial cells. The results indicate that BHA is a specific and potent inhibitor of rTNF-alpha- and rTNF-beta-induced cytotoxicity, as well as of rTNF-alpha-induced growth enhancement.

Animals↗
PubMed1992

Successful reversal of spontaneous diabetes in dogs by intraperitoneal microencapsulated islets.

Long-term euglycemia by intraperitoneal transplantation of microencapsulated islets has not been described in the diabetic large animal model. In this study, we report the successful long-term reversal of diabetes by this method in spontaneous diabetic dogs. We have identified fundamental mechanism(s) associated with alginate-based microcapsule fibrosis, and have devised methods to ameliorate this problem. These include the use of purified alginate of low mannuronic acid content and cytokine suppression. Ten insulin-dependent, spontaneous diabetic dogs (insulin requirement 1-4 units/kg/day; absence of circulating C-peptide and diabetic K-values of 0.6 +/- 0.4) were entered into the study. Islets from mongrel donor pancreata were isolated and transplanted intraperitoneally either as free islet controls (n = 3) or as microencapsulated islet allografts (n = 7). In all seven encapsulated islet recipients, euglycemia was achieved within 24 hr (serum glucose failing from 304 +/- 117 to 116 +/- 72 mg/dl). IVGTT performed 14 days after islet transplant demonstrated normalization of K-values changing from a pretransplant level of 0.6 +/- 0.4 to 2.6 +/- 0.6. All animals receiving encapsulated islets remained euglycemic, free of the need for exogenous insulin, for a period of 63-172 days, with a median insulin-independence for 105 days. In contrast, recipients receiving free islets rejected their graft within seven days of implantation. In conclusion, this is the first report of long-term successful reversal of spontaneous diabetes in the large animal model by an intraperitoneal injection of encapsulated islets. The potential exists for this form of therapy to be explored in the treatment of type I diabetes in man.

Animals↗