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T Hartung

Publications and source records attributed to T Hartung.

At least 37 records · Page 2Linked to original sources
PubMed2001

Structure-function relationship of cytokine induction by lipoteichoic acid from Staphylococcus aureus.

Lipoteichoic acids (LTAs) have been proposed as putative Gram-positive immunostimulatory counterparts to Gram-negative lipopolysaccharides. However, LTA from Staphylococcus aureus, the clinically most frequent Gram-positive pathogen, was inactive after purification. Here, a novel isolation procedure to prepare pure (>99%) biologically active LTA, allowing the first structural analysis by nuclear magnetic resonance and mass spectrometry, is described. A comparison with LTA purified by standard techniques revealed that alanine substituents are lost during standard purification, resulting in attenuated cytokine induction activity. In line with this finding, hydrolysis of alanine substituents of active LTA decimated cytokine induction. LTA represents a major immunostimulatory component of S. aureus.

Acetylglucosamine↗
PubMed2001

Dissociation of LPS-induced monocytic ex vivo production of granulocyte colony-stimulating factor (G-CSF) and TNF-alpha in patients with septic shock.

Over a 6 month period, in 192 patients admitted to the intensive care unit (ICU), a longitudinal analysis of whole blood lipopolysaccharide (LPS)-induced ex vivo cytokine production was performed on a daily basis until discharge from the ICU or death. Twenty-one patients with proven infections were in septic shock for the first time and for at least 3 days' duration. Ex vivo LPS-inducible release of granulocyte colony-stimulating factor (G-CSF) was upregulated and that of TNF-alpha was downregulated in patients with septic shock, regardless whether they survived or died. In conclusion, LPS-induced ex vivo TNF-alpha and G-CSF cytokine release by monocytes is regulated differentially in patients with septic shock. Since upregulation of LPS-induced production of G-CSF occurred earlier in survivors than in non-survivors, rapidly elevated and sustained G-CSF responsiveness may contribute to survival in septic shock.

Adult↗
PubMed2001

Immune protection against septic peritonitis in endotoxin-primed mice is related to reduced neutrophil apoptosis.

The innate immune system provides essential information about the presence of infectious danger and signals the activation and instruction of adaptive immunity. The present study addressed the question of whether prior exposure of the innate immune system to LPS may modulate host defense against acute septic peritonitis. We show that LPS priming 4 days, but not 2 days, prior to infection enhances bacterial clearance and improves survival of septic peritonitis. Immune protection in day 4 LPS-primed mice was specifically associated with a marked increase in the accumulation and activation of neutrophils at the site of infection. Accumulating neutrophils in day 4 LPS-primed mice exhibited a normal production of reactive oxygen metabolites in response to in vivo exposure to intestinal bacteria. The local increase in neutrophil numbers was found to result from a reduced rate of apoptotic cell death. Inhibition of neutrophil apoptosis in LPS-primed mice was mediated by soluble factor(s) distinct from G-CSF and GM-CSF. Thus, engagement of pattern recognition systems prior to infection may improve host defense by amplifying the effector cell response of innate immunity. The results also provide in vivo evidence that apoptosis of inflammatory cells represents an important process for the control of host defense to infection.

Animals↗
PubMed2001

Lipopolysaccharide and ceramide docking to CD14 provokes ligand-specific receptor clustering in rafts.

The glycosylphosphatidylinositol-anchored receptor CD14 plays a major role in the inflammatory response of monocytes to lipopolysaccharide. Here, we describe that ceramide, a constituent of atherogenic lipoproteins, binds to CD14 and induces clustering of CD14 to co-receptors in rafts. In resting cells, CD14 was associated with CD55, the Fcgamma-receptors CD32 and CD64 and the pentaspan CD47. Ceramide further recruited the complement receptor 3 (CD11b/CD18) and CD36 into proximity of CD14. Lipopolysaccharide, in addition, induced co-clustering with Toll-like receptor 4, Fcgamma-RIIIa (CD16a) and the tetraspanin CD81 while CD47 was dissociated. The different receptor complexes may be linked to ligand-specific cellular responses initiated by CD14.

Antigens, CD↗
PubMed2001

Improved innate immunity of endotoxin-tolerant mice increases resistance to Salmonella enterica serovar typhimurium infection despite attenuated cytokine response.

During infection with gram-negative bacteria, exposure of immune cells to lipopolysaccharide (LPS) from the bacterial cell membrane induces a rapid cytokine response which is essential for the activation of host defenses against the invading pathogens. Administration of LPS to mice induces a state of hyporesponsiveness, or tolerance, characterized by reduced cytokine production upon subsequent LPS challenge. In the model of experimental Salmonella enterica serovar Typhimurium infection of mice, we assessed the question of whether complete LPS tolerance induced by repetitive doses of LPS interfered with cytokine production and host defense against gram-negative bacteria. Although production of various cytokines in response to serovar Typhimurium was attenuated by LPS pretreatment, LPS-tolerant mice showed improved antibacterial activity, evidenced by a prolongation of survival and a continuously lower bacterial load. We attribute this protective effect to three independent mechanisms. (i) Peritoneal accumulation of leukocytes in the course of LPS pretreatment accounted for enhanced defense against serovar Typhimurium during the first 6 h of infection but not for decreased bacterial load in late-stage infection. (ii) LPS-tolerant mice had an increased capacity to recruit neutrophilic granulocytes during infection. (iii) LPS-tolerant mice showed threefold-increased Kupffer cell numbers, enhanced phagocytic activity of the liver, and strongly improved clearance of blood-borne serovar Typhimurium. These results demonstrate that despite attenuated cytokine response, acquired LPS tolerance is associated with enhanced resistance to infections by gram-negative bacteria and that this effect is mainly mediated by improved effector functions of the innate immune system.

Animals↗
PubMed2001

Modulation of cytokine release in ex vivo-stimulated blood from borreliosis patients.

In lipopolysaccharide-stimulated blood from 71 late-stage borreliosis patients, the ex vivo cytokine release capacity of tumor necrosis factor alpha (TNF-alpha) and gamma interferon (IFN-gamma) was reduced to 28% +/- 5% and to 31% +/- 5% (P < or = 0.001), respectively, compared to that of 24 healthy controls. White blood cell counts were normal in both groups. To investigate direct interactions between the pathogen and the immune cells, blood from healthy controls was exposed in vitro to live or heat-killed Borrelia or to Borrelia lysate. Compared to the pattern induced by bacterial endotoxins, a reduced release of TNF-alpha and IFN-gamma and an enhanced secretion of interleukin-10 and granulocyte colony-stimulating factor was found. In blood from 10 borreliosis patients stimulated with Borrelia lysate, TNF-alpha formation was decreased to 31% +/- 14% and IFN-gamma formation was decreased to 8% +/- 3% (P < or = 0.001) compared to the cytokine response of blood from healthy controls (n = 24). We propose to consider anti-inflammatory changes in the blood cytokine response capacity elicited by Borrelia as a condition that might favor the persistence of the spirochete.

Adolescent↗
PubMed2001

Mistletoe lectin-1 increases tumor necrosis factor-alpha release in lipopolysaccharide-stimulated whole blood via inhibition of interleukin-10 production.

We examined the immunomodulatory properties of the mistletoe preparation Lektinol (standardized for mistletoe lectin-1) and recombinant mistletoe lectin-1 (rML-1) in vitro by assessing alterations in the cytokine response of human whole blood. Lektinol or rML-1 alone did not induce any cytokine release in unstimulated whole blood. However, the lipopolysaccharide (LPS)-induced release of tumor necrosis factor (TNF)-alpha was increased, and the secretion of interleukin (IL)-10 was reduced by Lektinol at a mistletoe lectin-1 (ML-1) concentration of 0.5 to 5 ng/ml, whereas the LPS-induced secretion of IL-1 beta, IL-6, IL-12, and interferon-gamma was not affected. Lektinol did not alter the initial phase of TNF-alpha production but sustained TNF-alpha levels longer than in the LPS controls. Recombinant ML-1, but not the recombinant B-chain alone, also increased TNF-alpha release and decreased IL-10 release. We propose that the increase in TNF-alpha release is due to a specific inhibition of IL-10 release by Lektinol. This conclusion is based on the observation that blocking of endogenously formed IL-10 by a neutralizing antibody results in a similar increase of TNF-alpha in the late production phase after LPS stimulation. This hypothesis was also corroborated by the finding that when endogenously formed IL-10 was blocked, Lektinol could no longer increase TNF-alpha release. These results indicate that Lektinol modulates the cytokine response of human whole blood to LPS in a proinflammatory fashion, which can be attributed to ML-1.

Adjuvants, Immunologic↗
PubMed2000

Molecular mechanisms of high-dose antigen therapy in experimental autoimmune encephalomyelitis: rapid induction of Th1-type cytokines and inducible nitric oxide synthase.

High-dose Ag administration induces apoptotic death of autoreactive T cells and is an effective therapy of experimental autoimmune diseases of the nervous system. To explore the role of cytokines in Ag-specific immunotherapy, we analyzed mRNA induction and protein expression for the proinflammatory cytokines TNF-alpha and IFN-gamma, the anti-inflammatory cytokine IL-10, and the cytokine-inducible NO synthase (iNOS) during high-dose Ag therapy of adoptive transfer experimental autoimmune encephalomyelitis (AT-EAE) in the Lewis rat. Using semiquantitative and competitive RT-PCR, we found 5- to 6-fold induction of TNF-alpha mRNA and 3-fold induction of IFN-gamma mRNA in the spinal cord that occurred within 1 h after i.v. injection of Ag and was accompanied by a 2-fold increase of iNOS mRNA. Both IFN-gamma and iNOS mRNA remained elevated for at least 6 h, whereas TNF-alpha mRNA was already down-regulated 6 h after Ag injection. A comparable time course was found for circulating serum levels of TNF-alpha and IFN-gamma. IL-10 mRNA levels did not change significantly following Ag injection. Neutralization of TNF-alpha by anti-TNF-alpha antiserum in vivo led to a significant decrease in the rate of T cell and oligodendrocyte apoptosis induced by high-dose Ag administration, but did not change the beneficial clinical effect of Ag therapy. Our data suggest profound activation of proinflammatory but not of anti-inflammatory cytokine gene expression by high-dose Ag injection. Functionally, TNF-alpha contributes to increased apoptosis of both autoaggressive T cells and oligodendrocytes in the target organ and may thereby play a dual role in this model of Ag-specific therapy of CNS autoimmune diseases.

Animals↗
PubMed2000

cGMP-mediated inhibition of TNF-alpha production by the atrial natriuretic peptide in murine macrophages.

The atrial natriuretic peptide (ANP) is suggested to regulate inflammatory response by alteration of macrophage functions. The aim of this study was to investigate whether ANP influences production of TNF-alpha. TNF-alpha production in murine bone marrow-derived macrophages was induced by LPS, and TNF-alpha secretion (+/-ANP) was determined by L929 bioassay. ANP dose dependently (10-8-10-6 M) inhibited TNF-alpha release by up to 95%. The effect was mediated via the guanylate cyclase-coupled A receptor, as was shown by employing dibutyryl-cGMP, the cGMP-inhibitory compound Ly-83583, and the A receptor antagonist HS-142-1. A specific ligand of the natriuretic peptide "clearance" receptor inhibited TNF-alpha production only at 10-7 and 10-8 M, but not at 10-6 M. The B receptor ligand C-type natriuretic peptide showed no TNF-alpha-inhibitory effect. To investigate the underlying mechanism of ANP-mediated TNF-alpha inhibition, Northern blot was performed. ANP-treated macrophages displayed decreased TNF-alpha-mRNA levels. Besides the known inhibition of NF-kappaB activation, in this study we demonstrated that ANP also attenuates the activation of the proinflammatory transcription factor AP-1 (gel shift assay). ANP did not alter subunit composition of AP-1 complexes, as was shown by supershift assays applying anti-c-jun and anti-c-fos Abs. To get information on the ANP effect for human inflammatory processes, we investigated cytokine production in human LPS-activated blood. ANP significantly attenuated production of TNF-alpha and IL-1beta without affecting production of IL-10 and IL-1ra. In summary, ANP was shown to attenuate TNF-alpha production of LPS-activated macrophages via cGMP. The inhibition is suggested to involve transcriptional processes that are the result of reduced activation of responsible transcription factors.

Animals↗
PubMed2000

Effects of neutralizing antibodies to TNF-alpha on pain-related behavior and nerve regeneration in mice with chronic constriction injury.

Inhibition of proinflammatory cytokines reduces hyperalgesia in animal models of painful neuropathy. We set out to investigate the consequences of this treatment for nerve regeneration. Here we examined the sequels of epineurial application of neutralizing antibodies to tumor necrosis factor-alpha (TNF) in chronic constriction injury (CCI) of the sciatic nerve in C57/BL 6 mice. The mice were tested behaviorally for manifestations of thermal hyperalgesia and mechanical allodynia. Nerve regeneration was assessed by morphometry of myelinated nerve fibers in the sciatic nerve and of the epidermal innervation density in the glabrous skin of the hindpaws. Antibodies to TNF reduced thermal hyperalgesia and mechanical allodynia after CCI. Myelinated fiber density in the sciatic nerve was reduced to 30% of normal on day 7 after surgery, and reached 60% on day 45, with no difference between antibody-treated and untreated animals. Epidermal innervation density as shown by PGP 9.5 and CGRP immunohistochemistry was reduced to 25-47% at both time points after CCI, again without differences between antibody treated and untreated mice. Myelinated fiber density but not epidermal innervation density was correlated to thermal and mechanical withdrawal thresholds. We conclude that neutralization of endoneurial TNF attenuates pain related behavior but has no effect on nerve regeneration. Furthermore, the number of epidermal nerve fibers is not relevant to the magnitude of behavioral hyperalgesia in CCI.

Animals↗
PubMed2000

Human monocytes express functional receptors for granulocyte colony-stimulating factor that mediate suppression of monokines and interferon-gamma.

In a double-blind, placebo-controlled, randomized study, 10 healthy men received either a single dose of 480 microg granulocyte colony-stimulating factor (G-CSF) or saline. Blood taken from the volunteers was stimulated with 10 microg/mL endotoxin and released cytokines were measured by enzyme-linked immunosorbent assay. Expression of G-CSF receptors on leukocytes was examined by flow cytometry and reverse transcriptase-polymerase chain reaction. Functional activity of these receptors was tested by challenging isolated leukocyte populations to release cytokines with endotoxin in the presence of G-CSF. The G-CSF treatment attenuated the release of the proinflammatory cytokines tumor necrosis factor (TNF)-alpha, interleukin (IL)-12, IL-1beta, and interferon (IFN)-gamma in ex vivo lipopolysaccharide (LPS)-stimulated whole blood. In blood from untreated volunteers the presence of G-CSF in vitro also attenuated the LPS-stimulated release of these cytokines. G-CSF in vitro also attenuated TNF-alpha release from elutriation-purified monocytes. In the presence of 10 ng/mL recombinant TNF-alpha, the attenuation of LPS-inducible IFN-gamma release by G-CSF was blunted in whole blood. However, G-CSF had no such effect on IFN-gamma release from isolated lymphocytes stimulated with anti-CD3 or a combination of TNF-alpha and IL-12. G-CSF receptor expression was detected in human neutrophils and monocytes but not in lymphocytes by means of RT-PCR as well as flow cytometry. These results indicate that G-CSF receptors expressed on monocytes are functional in modulating monokine release. We conclude that the attenuation of IFN-gamma release from lymphocytes is not a direct effect of G-CSF on these cells but is rather due to the inhibition of monocytic IL-12 and TNF-alpha release by G-CSF. (Blood. 2000;95:270-276)

Adult↗
PubMed2000

Inflammatory and immunological parameters in children with haemolytic uremic syndrome (HUS) and gastroenteritis-pathophysiological and diagnostic clues.

The objective of this study was to identify parameters indicating a risk for developing typical haemolytic uremic syndrome (D+HUS) during the prodromal phase of diarrhea caused by enterohaemorrhagic Escherichia coli (EHEC). Forty-eight children were studied prospectively with regard to inflammatory serum factors on admission to hospital. Ten patients developed D+HUS (group I), 15 suffered from viral-gastroenteritis (group IIa) and 23 from other types of bacterial gastroenteritis (group IIb). Mean levels of IL-8 tended to be elevated in group I compared to groups IIa and IIb. Neopterin and IL-10 levels particularly were significantly decreased in HUS in comparison to both gastroenteritis groups. Low IL-10 levels indicate a substantial disregulation of the immune response in HUS, as IL-10 downregulates the pro-inflammatory response and suppresses pro-coagulant activity in experimental endotoxemia. Our results suggest low neopterin, high IL-8 and especially low IL-10 levels are indicators of a high risk for developing HUS.

Bacterial Infections↗
PubMed2000

Blood cytokine response of low-dose molgramostim (rhGM-CSF)-treated patients.

We examined leukocyte counts and ex vivo cytokine response of whole blood to lipopolysaccharide (LPS) or lipoteichoic acid (LTA) in patients under low-dose molgramostim therapy. Patients were injected subcutaneously daily for ten days with 1 microg/kg (n=9) or 2 microg/kg (n=14) molgramostim. Leukocytosis was observed in all patients, but only the eosinophil fraction was significantly increased in relation to other leukocyte populations. Ex vivo IFN-gamma release was decreased and IL-10 and IL-1ra secretion were increased in response to LPS or LTA. Thus, in non-neutropenic patients, leukocytosis can already be initiated by low doses of molgramostim. The ex vivo cytokine data suggest that these doses prime blood towards a systemic anti-inflammatory response.

Adult↗
PubMed2000

A new mechanism for IL-5-dependent helminth control: neutrophil accumulation and neutrophil-mediated worm encapsulation in murine filariasis are abolished in the absence of IL-5.

IL-5 production and eosinophilia are features of helminth infections, but results concerning the role of IL-5 and eosinophils (EP) in worm control are contradictory. We describe here a novel, IL-5-dependent mechanism of helminth control in vivo, using a fully permissive murine filariasis model, i.e. infection of BALB/c mice with Litomosoides sigmodontis. Worm control was exerted by the formation of inflammatory nodules around adult filariae which initially remained alive but were eventually killed within several weeks. The cell population essential for inflammatory nodule formation was found to be neutrophils (NP) but not EP. Neutralization of IL-5 led to a failure of both EP and NP accumulation at the site of infection (i.e. the thoracic cavity), resulting in cessation of inflammatory nodule formation around worms and in their survival. The role of NP in this process was confirmed by treatment of mice with anti-granulocyte colony stimulating factor (G-CSF) which also resulted in a lack of inflammatory nodule formation and worm killing albeit in the presence of EP. Since IL-5, due to the absence of IL-5 receptors on NP, does not act on these cells directly, it was investigated if anti-IL-5 altered the production of NP-chemotactic cytokines. In anti-IL-5-treated mice, cytokines known to promote NP accumulation like tumor necrosis factor-alpha, G-CSF and KC (IL-8) were found to be strongly reduced, while NP-deactivating cytokines like IL-10 were increased. In conclusion, IL-5 constitutes a cytokine essential for NP-mediated worm control in filarial infection.

Animals↗
PubMed2000

Role of TNF-alpha in high-dose antigen therapy in experimental autoimmune neuritis: inhibition of TNF-alpha by neutralizing antibodies reduces T-cell apoptosis and prevents liver necrosis.

TNF-alpha has been implicated as a potentially detrimental cytokine in autoimmune disorders of the nervous system and has been reported to be elevated in antigen-specific therapy of experimental autoimmune neuritis (EAN) in vivo. To investigate the role of TNF-alpha in EAN in rats that had been subjected to antigen-specific therapy with human P2 protein, animals were cotreated with an anti-TNF-alpha neutralizing antibody and the effects of the antibody on disease determined. Using this strategy in adoptive transfer (AT-) EAN, antigen-induced T-cell apoptosis in inflamed sciatic nerve and in liver was reduced to levels observed in control animals indicating that TNF-alpha mediates antigen-induced apoptosis of inflammatory T-cells. Focal liver necrosis, which had been observed in earlier studies after antigen therapy in AT-EAN, was prevented by passive immunization with neutralizing anti-TNF-alpha antibody. Unexpectedly, neutralization of TNF-alpha only partly abolished the protective effect of antigen therapy on the overall disease course. This may indicate that inhibition of TNF-alpha exerts beneficial effects other than through T-cell apoptosis, or that some of the benefit of antigen therapy is mediated by other pathways. These results indicate that secretion of TNF-alpha during antigen therapy has the dual potential to mediate beneficial apoptosis of inflammatory T-cells in the inflammatory lesion and to induce liver damage as a severe side effect.

Animals↗