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M Röllinghoff

Publications and source records attributed to M Röllinghoff.

At least 55 records · Page 3Linked to original sources
PubMed1998

IFN-gamma inhibits the production of latent transforming growth factor-beta1 by mouse inflammatory macrophages.

Transforming growth factor (TGF)-beta is a multifunctional cytokine, which in mammals exists in three isoforms (TGF-beta1, 2 and 3). It is synthesized by a variety of cells including macrophages, and exerts potent immunoregulatory effects such as the inhibition of Th1 development and the suppression or reversal of IFN-gamma-induced macrophage activation. In this study we analyzed the effect of IFN-gamma on the production of TGF-beta1 by thioglycolate-elicited mouse peritoneal macrophages under serum-free conditions. Untreated macrophages released TGF-beta1 in its latent form, which became detectable in a capture ELISA specific for active TGF-beta1 after acid activation of the culture supernatants. Treatment with IFN-gamma reduced the amount of latent TGF-beta1 in the culture supernatants in a dose-dependent fashion. The effect of IFN-gamma was confirmed by a newly developed Western blot system for the detection of mouse TGF-beta1 protein. IFN-gamma only weakly (16-24 %) reduced the levels TGF-beta1 mRNA at early and late time points of stimulation, and no evidence was obtained that IFN-gamma suppresses the secretion of latent TGF-beta1. Thus, inhibition of TGF-beta1 production by IFN-gamma is most likely due to decreased synthesis and/or stability of the TGF-beta1 protein, and might be important for the generation of fully activated macrophages and a Th1 response.

Animals↗
PubMed1998

The immune response to Leishmania: mechanisms of parasite control and evasion.

After transmission of Leishmania parasites by sandflies, disease manifestation of the infection requires mechanisms which allow the parasites to replicate in the mammalian host and to resist, at least initially, its innate and acquired antileishmanial defence. Likewise, lifelong persistence of Leishmania parasites, as it occurs even in cases of clinical healing of the infection, points to the existence of strategies which enable the parasite to partially circumvent the protective adaptive immune response of the host. In this review we will discuss the mechanisms which can be invoked to contribute to the initial, as well as long-term, survival of Leishmania parasites in the host organism. These include the passive protection of the parasite against antileishmanial products and the retreat into "safe target cells", the active suppression of the synthesis of reactive oxygen or nitrogen intermediates, the modulation of the host cytokine response, the inhibition of antigen-presentation and T cell-stimulation, and the induction and expansion of counterprotective T helper cells. It is probable that none of these mechanisms alone is sufficient to guarantee the survival of Leishmania, but together they might provide the safe environment which protects the parasite from elimination.

Animals↗
PubMed1998

Type 1 interferon (IFNalpha/beta) and type 2 nitric oxide synthase regulate the innate immune response to a protozoan parasite.

Type 2 nitric oxide synthase (NOS2) is required for the Th1-dependent healing of infections with intracellular microbes, including Leishmania major. Here, we demonstrate the expression and define the function of NOS2 during the innate response to L. major. At day 1 of infection, genetic deletion or functional inactivation of NOS2 abolished the IFNgamma and natural killer cell response, increased the expression of TGFbeta, and caused parasite spreading from the skin and lymph node to the spleen, liver, bone marrow, and lung. Induction of NOS2 was dependent on IFNalpha/beta. Neutralization of IFNalpha/beta mimicked the phenotype of NOS2-/- mice. Thus, IFNalpha/beta and NOS2 are critical regulators of the innate response to L. major.

Animals↗
PubMed1998

Analysis of cytokine patterns produced by individual CD4+ lymph node cells during experimental murine leishmaniasis in resistant and susceptible mice.

The concept of subdividing CD4+ T cells into Th0, Th1 and Th2 cells is based on the cytokine pattern produced by long-term in vitro cultured T cell lines. However, there exists uncertainty whether this classification can also be applied to CD4+ T cells in vivo. Herein it was investigated whether and at which frequency Th0, Th1 and Th2 cells are induced in vivo during an infection of mice with Leishmania major. Cytokine co-production in single IFN-gamma+ or IL-4+ CD4+ T cells as well as the frequency of such cells were assessed in the lymph nodes (LN) of infected mice. For this purpose, T cells derived from the draining LN were activated by phorbol myristate acetate (PMA)/ionomycin, and the intracellular cytokines IL-2, IL-4, IL-5, IL-10 and IFN-gamma were analyzed by immunofluorescence. One week after infection, a strong, but comparable increase of IFN-gamma+ CD4+ and IL-4+ CD4+ cells (up to 7% of all CD4+ cells) in the LN was observed in resistant C57BL/6 mice and susceptible BALB/c mice. IFN-gamma and IL-4 were not co-produced by single cells ('Th0 cells'). At later stages of the infection, the number of IL-4+ CD4+ cells decreased in C57BL/6, but not in BALB/c mice. All IL-4+ CD4+ cells showed an unexpected phenotype, because at least half of these cells co-produced IL-2, and the majority of the IL-4+ CD4+ did not co-produce the Th2 cytokines IL-5 and IL-10. Similar cytokine profiles were obtained when the CD4+ T cells were stimulated by Leishmania major-antigen instead of PMA/ionomycin. This study demonstrates that 'classical' Th1 cells (IFN-gamma+IL-2+), but no 'classical' Th2 cells (IL-4+IL-5+IL-10+) and no Th0 cells (IFN-gamma+IL-4+) are generated during L. major infection of mice in vivo.

Animals↗
PubMed1998

Antrum- and corpus mucosa-infiltrating CD4(+) lymphocytes in Helicobacter pylori gastritis display a Th1 phenotype.

In this study, cytokine patterns produced by CD4(+) T cells isolated from antrum or corpus gastral biopsy specimens of 10 patients with Helicobacter pylori-positive gastritis were compared. To this end, expression of intracellular cytokines (interleukin-4 [IL-4] and gamma interferon) and of CD4 was assessed by flow cytometry. Ten to 60% of the isolated CD4(+) T cells produced gamma interferon upon stimulation. With the exception of one patient, IL-4-positive CD4(+) cells were not detected. Therefore, CD4(+) cells infiltrating antrum and corpus stomach mucosa during H. pylori infection show a Th1 phenotype. This polarized Th1-type response may contribute to the inability of the immune system to eradicate H. pylori infection.

Adult↗
PubMed1998

Effective and long-lasting immunity against the parasite Leishmania major in CD8-deficient mice.

The results of earlier investigations that tested whether CD8(+) T cells are required in the defense against Leishmania major have been inconsistent. We used CD8-deficient mice to directly address this issue. After primary infection with L. major, CD8-deficient mice controlled the infection for over 1 year and mounted strong T helper 1 cell responses. Thus, CD8(+) T cells are not required for the long-term control of a primary infection with L. major.

Animals↗
PubMed1998

The Th1/Th2 paradigm and experimental murine leishmaniasis.

In recent years, the Th1/Th2 concept has become of prime importance in the understanding of heterogeneous responses of the immune system and implications thereof for infectious and autoimmune diseases. Originally established on the basis of different cytokines produced by T cell clones, it is now known that the Th1/Th2 concept really defines totally different immune pathways that affect most if not all cells of the immune system. Murine experimental leishmaniasis was the first model to confirm the relevance of the Th1/Th2 concept in vivo. Herein, we summarize the current knowledge on the characteristics and generation of Th1 and Th2 cells, as well as on recent advances of the application of this concept to murine cutaneous leishmaniasis.

Animals↗
PubMed1998

Experimental murine leishmaniasis and the Th1/Th2 cell concept.

Herein, the current knowledge about the immune response during murine cutaneous leishmaniasis is summarized. Special regard is given to the characteristics and generation of Th1 and Th2 cells during this disease. Originally established on the basis of different cytokines produced by T cell clones, it is now known that the Th1/Th2 concept really defines totally different immune pathways that affect most, if not all cells of the immune system. Murine experimental leishmaniasis was the first model to confirm the relevance of the Th1/Th2 concept in vivo. In particular, data from this laboratory will be presented on the role of different IL-4 receptor allotypes, on the role of the transcription factor interferon-regulatory-factor-1 (IRF-1) and the importance of the enzyme inducible NO synthase (iNOS). This work was supported by the SFB 263 and the Fonds der Chemischen Industrie.

Animals↗
PubMed1997

Molecular characterization and functional analysis of murine interleukin 4 receptor allotypes.

The murine interleukin 4 receptor (IL-4R) exists as a transmembrane protein transducing pleiotropic IL-4 functions, or as soluble (s)IL-4-binding molecule with potent immunoregulatory effects. In this study we identified and characterized a murine IL-4R allotype. Sequence analysis of the IL-4R cDNA of BALB/c mice revealed 18 base substitutions leading to three extracellular and five cytoplasmic amino acid changes when compared with the published IL-4R sequence of C57BL/6 mice. Analyses with allotype-specific mAbs revealed that AKR/J and SJL/J mice possess the newly identified BALB/c IL-4R allotype whereas the IL-4Rs of C3H, CBA, DBA-2, and FVB/N mice are identical to that of the C57BL/6 mouse. The extracellular Thr49 to Ile substitution abrogates one N-glycosylation site in the naturally occurring BALB/c IL-4R as well as in the experimentally point mutated C57BL/6-T49I sIL-4R, and both molecules display a nearly threefold reduction in IL-4-neutralizing activity compared to the C57BL/6 sIL-4R. In line with this, a significantly enhanced dissociation rate of IL-4 was detected for the BALB/c IL-4R allotype by surface plasmon resonance and in radioligand binding studies with IL-4R-transfected cell lines. These findings suggest that the altered ligand binding behavior of the newly described IL-4R allotype may influence the IL-4 responsiveness, thus contributing to the diverse phenotypes of inbred mouse strains in IL-4-dependent diseases.

Alleles↗
PubMed1997

Mechanism of suppression of macrophage nitric oxide release by IL-13: influence of the macrophage population.

IL-13 is a cytokine produced by T lymphocytes, mast cells, basophils, and certain B cell lines that up-regulates or inhibits various macrophage functions. In the present study we analyzed the mechanisms of suppression of nitric oxide (NO) release by IL-13 in the macrophage cell line J774A.1 and in thioglycolate-elicited mouse peritoneal macrophages. In both cell types efficient reduction (>80%) of NO production required treatment of the macrophages with IL-13 for at least 7 h before stimulation with IFN-gamma and LPS. In J774A.1 cells, increasing concentrations of IFN-gamma partially antagonized the suppression mediated by IL-13, whereas in peritoneal macrophages, the inhibitory effect of IL-13 was largely independent of the concentrations of IFN-gamma and LPS. In J774A.1 cells, IL-13 strongly reduced both the mRNA and protein levels of inducible nitric oxide synthase (iNOS, NOS-2), as determined by Northern blot analysis and immunoprecipitation. In peritoneal macrophages, in contrast, IL-13 decreased iNOS protein and enzyme activities after 8 to 48 h of stimulation, without altering the expression of iNOS mRNA. Pulse labeling with [35S]methionine revealed that IL-13 caused a 4.7-fold reduction of the de novo synthesis of iNOS protein in these cells. These data demonstrate for the first time that IL-13 is capable of regulating iNOS at both the mRNA and translational levels and underline the important influence of the macrophage population when studying mechanisms of cytokine functions.

Animals↗
PubMed1997

In vivo blocking of L-selectin rescues BALB/c mice from fatal Leishmania major infection.

Susceptibility and resistance to experimental Leishmania major (L. major) infection in mice are associated with a Th2- or Th1-type response, respectively. We have previously shown that immunological events occurring within the first 24 h after infection in the lymph node (LN) draining the site of parasite challenge are critical for the development of either type of T-cell responses. In the present study we manipulated these events by preventing the entry of naive lymphocytes into the draining LN by injecting BALB/c mice with a single dose of the anti-L-selectin mAb MEL-14 one day prior to infection with L. major. In contrast to control BALB/c mice, in MEL-14 treated animals the primary lesion healed 12 weeks after infection. The parasite load in the spleen and lymph nodes of MEL-14 treated mice was significantly reduced. The healing was found to be associated with an increased production of IFN-gamma and with a decrease in IL-4 production by LN cells. We observed a dramatic decrease in cellularity in the draining LN in Mel-14 treated L. major-infected mice within the first week of infection. Moreover, the cells in the LN of MEL-14 treated mice were highly enriched in activated cells as well as in cell influx in the draining LN after local L. major infection of BALB/c mice prevents fatal disease. The data suggest the MEL-14-induced enrichment of the draining LN in memory and activated cells is fundamental for the initiation of a protective Th1-type response.

Animals↗
PubMed1997

Control of Leishmania major infection in BALB/c mice by inhibition of early lymphocyte entry into peripheral lymph nodes.

A single i.p. injection with the anti-CD62L (anti-L-selectin) mAb Mel-14 before parasite challenge protected BALB/c mice from the otherwise lethal infection with Leishmania major. The Mel-14 mAb treatment resulted in a significant (>90%) decrease in cellularity of the popliteal lymph node (PLN) with a decrease in the proportion of CD4+ cells and an increase of the proportion of B220+ cells. Furthermore, both activated cells (CD25+ and CD69+) and cells of the memory phenotype (CD45RBdull CD44high) were significantly enriched in PLN from Mel-14-treated BALB/c mice. After infection with L. major, the otherwise massive cellular infiltration in the draining PLN was completely blocked in the Mel-14-treated mice, and in these animals the high representation of both activated and memory cells in PLN remained characteristic for the first days of infection. The protective effect was found to be associated with a markedly increased production of IFN-gamma and with a decrease in IL-4 production upon restimulation of PLN and spleen cells with L. major Ag in vitro. The cured mice were found to be resistant against a secondary challenge with the parasites. These data suggest that the induction of a nonprotective Th2 response to L. major is associated with the entry of lymphocytes from the recirculating pool into the draining LN. The Mel-14-induced changes in the lymphoid microenvironment of the draining peripheral LN appear to favor the development of a protective Th1 cell-mediated immune response against the parasite.

Animals↗
PubMed1997

Tumor necrosis factor-alpha expression induced by anti-YopB antibodies coincides with protection against Yersinia enterocolitica infection in mice.

Previous studies have suggested that virulence of pathogenic Yersiniae is associated with a suppression of the local cytokine response. In this context, the plasmid-encoded 41-kDa Yersinia outer protein B (YopB) has been implicated with the lack of tumor necrosis factor-alpha (TNF-alpha) expression in Peyer's patches (PP), following oral infection of mice with the enteropathogenic Yersinia enterocolitica. The present study was performed to further evaluate the relationships between YopB-induced suppression of TNF-alpha and bacterial survival in host tissue. Results are presented to show the ability of purified YopB to suppress the release of TNF-alpha by macrophages, the effect of which was neutralized by monospecific anti-YopB antiserum. In mice orally infected with Y. enterocolitica, anti-YopB treatment on days 3 and 5 postinfection, significantly decreased the recovery of live bacteria from PP. This observation correlated with a strong increase in TNF-alpha expression, as determined by reverse transcription-polymerase chain reaction and measuring the levels of TNF activity in homogenates of PP. Moreover, treatment of mice with a combination of anti-YopB and anti-TNF-alpha antiserum, completely abrogated the beneficial effect of the anti-YopB antiserum. In controls, expression of other proinflammatory cytokines such as interleukin-1 remained unaffected by either treatment. Therefore, the results indicate that endogenous TNF-alpha is required for eradication of Y. enterocolitica from host tissue, and further imply that YopB significantly contributes to suppression of the local TNF-alpha response in PP.

Animals↗
PubMed1997

Host-cell cyclophilin is important for the intracellular replication of Leishmania major.

The antiparasitic effects of cyclosporin A were examined in leishmanial infection by analysing the role of CsA-binding proteins (cyclophilins) in the host-parasite interaction. We hypothesized that the leishmanicidal effects of CsA on Leishmania major infected macrophages might be mediated through a cyclophilin of either the parasite or the host cell. Two cyclophilins (20 and 22 kDa) were purified from L. major parasites and N-terminally sequenced. Although enzyme activity of these cyclophilins was inhibited by CsA, pretreatment of L. major parasites with CsA did not result in reduction of a subsequent macrophage infection, arguing against a role of L. major cyclophilins as infectivity potentiators. However, host-cell cyclophilin A (CypA) was found to be critically involved in the intracellular replication of L. major parasites in murine macrophages. An antisense oligonucleotide to murine CypA was constructed and added to cultures of peritoneal macrophages prior to infection with L. major parasites. This treatment strongly reduced the expression of CypA in macrophages and resulted in the inhibition of the intracellular replication of L. major amastigotes. These data indicate that interaction of amastigotes with host-cell cyclophilin is an important part of the intracellular replication machinery of L. major and define, for the first time, a direct involvement of a cyclophilin in the survival strategies of an intracellular parasite.

Amino Acid Isomerases↗
PubMed1997

Derepressed hyphal growth and reduced virulence in a VH1 family-related protein phosphatase mutant of the human pathogen Candida albicans.

Mitogen-activated protein (MAP) kinases are pivotal components of eukaryotic signaling cascades. Phosphorylation of tyrosine and threonine residues activates MAP kinases, but either dual-specificity or monospecificity phosphatases can inactivate them. The Candida albicans CPP1 gene, a structural member of the VH1 family of dual- specificity phosphatases, was previously cloned by its ability to block the pheromone response MAP kinase cascade in Saccharomyces cerevisiae. Cpp1p inactivated mammalian MAP kinases in vitro and acted as a tyrosine-specific enzyme. In C. albicans a MAP kinase cascade can trigger the transition from the budding yeast form to a more invasive filamentous form. Disruption of the CPP1 gene in C. albicans derepressed the yeast to hyphal transition at ambient temperatures, on solid surfaces. A hyphal growth rate defect under physiological conditions in vitro was also observed and could explain a reduction in virulence associated with reduced fungal burden in the kidneys seen in a systemic mouse model. A hyper-hyphal pathway may thus have some detrimental effects on C. albicans cells. Disruption of the MAP kinase homologue CEK1 suppressed the morphological effects of the CPP1 disruption in C. albicans. The results presented here demonstrate the biological importance of a tyrosine phosphatase in cell-fate decisions and virulence in C. albicans.

Amino Acid Sequence↗
PubMed1997

A dominant mechanism coordinately suppresses the expression of Th2 lymphokines.

This study, we present evidence for a negatively acting control mechanism that coordinately suppresses the synthesis of the Th2 lymphokines IL-4, IL-5 and IL-6. This control mechanism operates in the murine thymoma cell line BW 5147. When cells of this line were fused to four independently established, well-defined Th2 cell clones, all resulting 74 lymphokine-secreting hybridomas secreted IL-2 which was not secreted by any of the parental Th2 cell clones. Most interestingly, however, none of the 74 hybridomas retained the capacity of the parental Th2 cells to express IL-4. Likewise, the secretion of IL-5 and IL-6 was also suppressed. Obviously, BW 5147 cells dominated the pattern of lymphokines produced, although the lymphokine pattern of Th2 cells was previously considered to be irreversibly fixed due to terminal differentiation of these cells. Suppression of IL-4 production was also observed at the mRNA level, as tested in Northern blot assays. Putative DNA target sequences for suppression of IL-4 gene transcription were not part of the proximal IL-4 promotor regions. Remote DNA control sequences may exist which coordinately regulate the proper, stage-specific expression of the Th2 lymphokines IL-4, IL-5 and IL-6.

Animals↗
PubMed1997

Bacterial cytokine antagonists encoded by pathogenic yersiniae.

Proinflammatory cytokines such as tumor necrosis factor alpha (TNF alpha) are important immunoregulatory mediators of the antibacterial host defense. Previous studies have suggested that virulence of pathogenic Yersiniae is associated with suppression of the local cytokine response. In this context, the plasmid-encoded 41 kDa Yersinia outer protein B (YopB) has been implicated with a lack of TNF alpha expression in Peyer's Patches (PP), following oral infection of mice with the enteropathogenic Yersinia enterocolitica. The present study was performed to further evaluate the relationships between YopB-induced suppression of TNF alpha and bacterial survival in host tissue. Results are presented to show the ability of purified YopB to suppress the release of TNF alpha by macrophages. In mice orally infected with Y. enterocolitica, anti-YopB treatment on days 3 and 5 postinfection, significantly decreased the recovery of live bacteria from PP. This observation correlated with a strong increase in TNF alpha expression, as determined by RT-PCR and measuring the levels of TNF activity in homogenates of PP. Moreover, treatment of mice with a combination of anti YopB and anti-TNF alpha antiserum, completely abrogated the beneficial effect of the anti-YopB antiserum. In controls, expression of other proinflammatory cytokines such as IL-1 remained unaffected by either treatment. Therefore, the results indicate that endogenous TNF alpha is required for eradication of Y. enterocolitica from host tissue and further imply that YopB significantly contributes to suppression of the local TNF alpha response in PP.

Animals↗