Mycobacterial nucleic acids in sarcoid lesions.
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DNA, Bacterial↗
Biomedical subjects
M Schlaak
Publications and source records attributed to M Schlaak.
Modulation of tumor cell susceptibility to cytokine-induced cell death by hormones, growth factors, and cell density.
The mechanisms controlling "spontaneous" cellular death rates in normal and tumorigenic tissues are largely unknown. An important parameter in this respect is the susceptibility of the target cell to induction of the lytic pathway by appropriate signals. In the present article it is demonstrated in a serum-free in vitro system that the susceptibility of human tumor cells (TC) to induction of lysis by cytokine signals generated during interaction of TC with elutriated human monocytes (MO) is a highly dynamic parameter subject to modulation by hormones, growth factors, and tumor cell density. It was found that growth stimulatory signals such as insulin, and especially epidermal growth factor (EGF), increase lytic susceptibility, whereas hydrocortisone, which does not exert significant growth modulatory effects in these examples, protects TC against the induction of lysis. Increasing TC density above confluence dramatically enhances lytic susceptibility, suggesting interactions between TC to be involved in the induction of their death. In conjunction with previous data demonstrating the insusceptibility of TC, which are forced out of the cell cycle into the quiescent state (G0), the hypothesis is put forward that growth stimulatory factors increase a TC's lytic susceptibility by preventing its transit from G1 to G0 in response to growth inhibitory signals generated during MO/TC interaction. The data support the concept that TC susceptibility to the induction of cell death is a consequence of simultaneously activated growth stimulatory and growth inhibitory signalling pathways.
Cell Communication↗
Cytokines involved in monocyte mediated tumor cell death and growth inhibition in serum-free medium.
In a serum-free culture system, the release of TNF, lI-1, lI-6, IFN-alpha, and IFN-beta during interaction of elutriated human monocytes (MO) with human tumor cells (TC) was studied by ELISA-technique. Contributions of these cytokines to inhibition of TC-growth and to induction of TC-death by supernatants (SU) gained from such MO/TC-interaction cultures were investigated using affinity chromatography for removal of individual cytokines. Although the TC used are relatively insensitive to recombinant human TNF, withdrawal of TNF causes 50% to 75% reduction of SU-induced TC-death rates, suggesting that susceptibility to TNF is raised during MO/TC-interaction by the other cytokines. Individual removal of other cytokines does not cause reduction of SU-mediated TC-death. However, combined withdrawal of lI-1 and IFN-alpha/beta causes in 2 of 4 TC-lines significant reduction of TC-death. Combined removal of TNF, IFN-alpha/beta, lI-1, and lI-6 leads to complete prevention of SU-mediated growth inhibitory and lytic effects, suggesting that besides these cytokines other signals are not involved significantly. SU-effects can be mimicked by appropriate combinations of authentic cytokines. The response of TC to SU- or cytokine-exposure is strikingly dependent on TC-density, leading at subconfluent TC-density exclusively to inhibition of growth and at postconfluent TC-density to induction of cell death. The principal effect of SU or cytokine combinations in this context seems to be the activation of growth inhibitory signal transduction pathways leading to TC-death in postconfluent TC-populations exclusively if growth stimulatory pathways are activated at the same time. Mouse L cells do not follow this reaction pattern: Their death is exclusively dependent on the presence of TNF in SU and they die upon SU-exposure at postconfluent as well as at subconfluent cell density.
Animals↗
Epitope analysis of the allergen ovalbumin (Gal d II) with monoclonal antibodies and patients' IgE.
Ovalbumin (OVA) is a major allergen (Gal d II) of hen egg white and is often the cause of hypersensitivity reactions to food. Further knowledge of the antigenic and allergenic epitopes of allergens will provide better treatment of this disease. To analyse these epitopes we produced a panel of monoclonal antibodies (mAbs) against native OVA. The initial information about the epitopes was obtained with the binding patterns of these mAbs in IEF-immunoprints and western blots of OVA under reducing and non-reducing conditions. It was possible to demonstrate that the different conformations of OVA exhibit different epitopes, and that there are other epitopes which are shared by each conformation. Seven different, although sometimes overlapping epitopes, could be determined on native OVA; four different epitopes on denaturated non-reduced OVA by means of immunoblots of the intact molecule. The number of epitopes which could be differentiated by the mAbs was increased by the use of peptide blots after CNBr fragmentation of the molecule. IgE binding to different OVA conformations and to CNBr-fragments of OVA was also detectable and appears in the same regions as the reactivity of some mAbs. Western blots of OVA and CNBr-peptides demonstrate that some antigenic/allergenic binding sites seem at least partly to be continuous epitopes. The identification of the CNBr-fragments was performed by a microsequence analysis of blotted CNBr-fragments after a 2-dimensional electrophoresis. IgE was found to bind the two largest CNBr-fragments (residues 41-172 and 301-385), but not the fragment corresponding to residues 173-196. A number of monoclonal antibodies also reacted with the two large fragments, especially with fragment 301-385, and some bind also to shorter peptides, such as fragment 173-196, which were not reactive to patients' IgE. Most of the monoclonal antibodies and patients' IgE bind to the fragments 41-172 and 301-385 in 2D-PAGE blots suggesting that these fragments are involved in an immunogenic structure.
Amino Acid Sequence↗
Characterization of isoforms of the major allergen Phl p V by two-dimensional immunoblotting and microsequencing.
Timothy pollen extract was separated by 2D PAGE blot for further characterization of the major allergen Phl p V. Using pooled patient serum, we demonstrated that Phl p V consists of 4 components at 32 kD and 4 components at 38 kD, each differing in their pIs. The primary structure and the amino acid composition of the 8 proteins were determined form the blotted samples. Proteins of the same molecular weight did not differ in the 20 N-terminal amino acid residues, whereas the 32- and 38-kD proteins showed only 60% sequence identity. Furthermore, the results of the amino acid analyses suggest differences in their protein structure. Therefore, it might be possible that both proteins express different IgE-reactive epitopes.
Allergens↗
Detection of IgE antibodies specific for 1-phenyl-2,3-dimethyl-3-pyrazoline-5-one by RAST: a serological diagnostic method for sensitivity to pyrazoline drugs.
Certain adverse reactions to pyrazoline drugs resemble IgE-mediated hypersensitivity. However, convincing evidence of antigen-antibody interactions is not fully demonstrated. In this study, IgE antibodies specific for 1-phenyl-2,3-dimethyl-3-pyrazoline-5-one have been found in 17 out of 19 serum samples from individuals sensitive to pyrazoline drugs with 4-aminoantipyrine discs by Radio Allergo Sorbent Test (RAST). In contrast, we have not found any positive results from 10 normal donors without sensitivity to pyrazoline drugs after ingestion of metamizol 500 mg/day for 14 days. Therefore, our results provide further evidence in favor of an IgE-dependent mechanism in patients suffering from sensitivity to pyrazoline drugs. The determination of specific IgE antibodies could be used as a serodiagnostics method.
Adult↗
The presence of specific IgE to salicyloyl and O-methylsalicyloyl in aspirin-sensitive patients.
Certain adverse reactions to aspirin (ASA), nonsteroidal anti-inflammatory drugs (NSAIDs) and pyrazoline derivatives resemble IgE-mediated hypersensitivity. However, convincing evidence of antigen-antibody interactions or of the inhibition of the cyclooxygenase pathway of arachidonic acid metabolism leading to an increase in the generation of leukotrienes (LTs) and a decrease in the generation of prostaglandins (PGs) was not fully demonstrated. In this study, two types of specific IgE antibodies have been found in 27 serum samples from 28 ASA-sensitive patients with salicyloyl-discs and O-methylsalicyloyl-discs by Radio Allergo Sorbent Tests (RAST). The positive rates were 96.4% and 71.4%, respectively. In contrast, no positive results could be found in 10 normal donors without ASA sensitivity after ingestion of ASA 500 mg/day for 14 days. Further investigation of the chemical structure of epitopes was done by cross inhibition studies. Our results are an increasing evidence in favour of an IgE-dependent mechanism in patients suffering from ASA sensitivity. Hopefully, the determination of specific IgE antibodies will be a safe diagnostic method of ASA sensitivity in vitro.
Adult↗
[Pentoxifylline--an inhibitor of the synthesis of tumor necrosis factor alpha].
The growing knowledge on the pathophysiological role of cytokines in acute and chronic inflammatory processes stimulated efforts to control their synthesis and action pharmacologically in clinical situations. Recently, in our institute evidence was raised that pentoxifylline (POF) is able to suppress the synthesis of tumor necrosis factor-alpha (TNF) in cell cultures, in vivo, and to protect experimental animals against endotoxin shock. Studies in human experimental endotoxemia showed that pentoxifylline decreased circulating TNF without affecting endogenous formation of interleukins. The potency of this drug to interfere with TNF synthesis could also be demonstrated in cases of acute and chronic cytokine release syndromes such as OKT3 first-dose reaction and severe pulmonary tuberculosis, respectively. We suggest that POF may improve therapeutic strategies in various diseases in which TNF was identified as a causative pathophysiological factor.
Adult↗
[Atypical mycobacterial infections].
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Humans↗
Suppression of tumor cell susceptibility to monocyte-induced cell death by growth-inhibitory signals generated during monocyte/tumor cell interaction.
In a recently established serum-free in vitro system it has been demonstrated that the susceptibility of various human tumor cells to the induction of cell death by elutriated human monocytes is critically dependent on tumor cell density and growth state. In the present work it is shown by flow cytofluorometric analysis of bromodeoxyuridine incorporation rates and of expression of the proliferation-associated nuclear antigen Ki-67, that tumor cells forced out of the cell cycle into the quiescent state (G0), which can be accomplished by treatment with supernatant from monocyte/tumor cell interaction cultures, are no longer susceptible to the induction of cell death by monocytes. This suggests that processes essential for the lytic pathway cannot take place in quiescent cells. It is furthermore demonstrated that tumor cells are driven into G0 during interaction with monocytes and that the rate of transit from G1 to G0 increases with increasing monocyte dosage. This explains our earlier finding that maximum rates of tumor cell death are induced at rather low monocyte:tumor cell ratios of around 1:2 and that lysis is suppressed at higher monocyte dosages (van der Bosch et al.:Exp Cell Res 187:185-192, 1990). The potential significance of these findings for the supposed function of mononuclear phagocytes in tumor defense lies in the notion that tumor cells driven into G0 might escape this control and that signals involved in monocyte/tumor cell-interaction contribute to the accumulation of tumor cells in G0.
Cell Communication↗
Cyclosporin for hypereosinophilic syndrome.
The idiopathic hypereosinophilic syndrome (HES) comprises a heterogeneous group of disorders with unknown pathogenesis characterized by persistent peripheral blood and bone marrow eosinophilia and eosinophil infiltrates of multiple organs, leading to severe organ dysfunction. Lymphokine-mediated T-lymphocyte control of human eosinophilic granulopoiesis is though to play a major role in the pathogenesis of HES. Treatment of this disease with cyclosporin-A (CSA) therefore appears to be sensible. We report the case of a patient with a severe HES who failed to respond adequately to glucocorticoid treatment. With additional CSA therapy, disease activity showed a favorable remission and eosinophil counts rapidly decreased to the normal range and remained normal even after reduction of the methylprednisolone dosage to 7.5 mg daily. To date his remission has continued for more than 6 months. In the meantime we have confirmed the beneficial effects of CSA in two other cases of HES. This suggests that CSA treatment is justified, at least in combination with glucocorticoids, in severe cases of HES to prevent the side effects of a long-lasting high-dose glucocorticoid therapy.
Adult↗
Monocyte-mediated growth control and the induction of tumor cell death.
In the present article a hypothesis is put forward and supporting data are referred that explain the elimination of tumorigenic cells as a consequence of their failure to comply with the rules of ubiquitous negative growth control mechanisms involving among others also mononuclear phagocytes as effector cells. This hypothesis does not invoke the recognition of altered cell surface structures on tumorigenic cells as the basis for discriminating them from normal cells and thus avoids one of the most irritating problems of hypothetical tumor defense mechanisms involving the recognition of spontaneously arising tumor cells as 'non-self' by immunologic effector cells.
Animals↗
Release of mediators from human gastric mucosa and blood in adverse reactions to benzoate.
A study was carried out on 29 patients to investigate the amount of histamine liberation and release of platelet-activating factor and 6-keto-prostaglandin F1 alpha from gastric mucosa and whole blood or mononuclear cells by sodium benzoate. The patients suffered from asthma (10), atopic dermatitis (7) and chronic urticaria (4). 8 patients with unrelated, non-immunologic diseases served as controls. In the oral provocation test (OPT) 3 patients experienced a recurrence of their original disease, whilst 1 asthmatic patient reacted with abdominal disorder. The release of histamine and prostaglandin from mucosa was significantly increased by sodium benzoate in comparison to the spontaneous release observed in patients. The mucosa of the control persons did not react to sodium benzoate. Furthermore, there was a significant difference in prostaglandin release between patients with positive OPT and the control persons. No difference could be found between patients with negative OPT and those with positive OPT. Additionally, in the mediator release from whole blood or mononuclear cells there was no obvious difference apparent. These results suggest a possible involvement of prostacyclin and histamine in adverse reactions to benzoate. Due to the sensitivity of the method, a mediator release from mucosa can already be demonstrated in a preclinical state of the pseudoallergic reaction in the absence of clinical symptoms.
6-Ketoprostaglandin F1 alpha↗
Prevalence and subclass distribution of IgG-anti-IgE autoantibodies in atopy and parasitosis.
Using immunoblotting, we investigated sera of 60 patients with atopic dermatitis, 12 patients with helminth infections and 36 nonallergic controls, for anti-IgE autoantibodies. We found IgG anti-IgE autoantibodies in 62% of the atopics, 42% of the patients with parasitosis and 11% of the controls. IgG anti-IgE occurred most often (94%) in patients with atopic dermatitis plus additional atopic disorder, such as allergic asthma and rhinoconjunctivitis. In parallel, we found a significantly higher occurrence of IgG anti-IgE in the patients with high IgE levels compared to patients with low IgE levels (p less than 0.0005). The predominant subclasses of anti-IgE autoantibodies were IgG1 and IgG3 in atopy and parasitosis. In the controls, we found IgG4 and IgG3 anti-IgE, but no IgG1 autoantibodies. The frequency of IgG2 anti-IgE was very low; it occurred in 2 patients only. Prevalence and IgG subclass distribution of anti-IgE autoantibodies was found to be different for patients with atopic dermatitis, parasitic infection and for controls.
Antibodies, Anti-Idiotypic↗
Epitope mapping of allergens and antigens of timothy pollen extract.
For the identification of allergens in crude timothy pollen extract, 2D immunoblotting was performed with subsequent use of patients' IgE. Only about 15 of more than 70 detectable components with molecular weights of 55, 38, 35, and 32 kD showed IgE-reactivity. The 55 and 35 kD allergens were identified as glycoproteins by a glycan detection kit. To investigate the protein structure of the allergens, proteins of the pollen extract were cleaved by CNBr and endoproteinases. The cleavage products were identified by patients' IgE and monoclonal antibodies (moab) raised against timothy pollen proteins. While the use of endoproteinases resulted in a complete loss of some allergens, CNBr produced smaller IgE-reactive proteins, e.g. the 38 kD component was split into a 32 kD component and the original 32 kD protein was partially cleaved into IgE-reactive fragments of 30, 21, and 15 kD. In order to investigate the IgE-binding epitopes we intend to determine the amino acid sequence of the cleavage products.
Allergens↗
Effects of pentoxifylline in endotoxinemia in human volunteers.
The following effects of pentoxifylline in endotoxinemia in man could be demonstrated: 1. Il-6 release and Il-6 mediated effects such as clinical responses and leukocytosis are not inhibited by POF treatment. 2. TNF-alpha release is suppressed which might be the most important result, because TNF seems to play the major role in the pathophysiological events of endotoxinemia. Furthermore, pentoxifylline is able to counteract the initial leukocytopenia caused by sticking of leukocytes in the microcirculation. 3. De-novo-synthesis of cytokines by monocytes ex vivo is totally abolished. This may possibly reflect the in vivo situation. In conclusion, beneficial effects of pentoxifylline in respiratory distress syndrome, multi-organ failure and septic shock are suggested. Furthermore, our data indicate that endotoxin-induced formation of Il-6 and TNF-alpha are regulated independently in vivo.
Endotoxins↗
Circadian rhythm of interleukin-1 production of monocytes and the influence of endogenous and exogenous glucocorticoids in man.
We found a dose-dependent inhibition of spontaneous and LPS-induced IL-1 production of isolated human monocytes by methylprednisolone (MP) in vitro. Kinetic studies of spontaneous and LPS-induced IL-1 production of isolated monocytes of 10 normal individuals showed a synchronous circadian rhythm, with its maximum at 4:00 p.m. and its minimum at 4:00 a.m., which is most probably independent of the physiological circadian rhythm of cortisol levels because the IL-1 production was of the same value at the times of maximum and minimum cortisol levels. In contrast, in a patient with hypercortisolism and a preserved circadian rhythm of cortisol levels, we found the minimum of IL-1 production at 4:00 p.m., 8 hours after the maximum cortisol level was reached. Furthermore, in 7 patients with sarcoidosis both spontaneous and LPS-induced IL-1 production of isolated monocytes were significantly decreased 8 hours after the first injection of MP (1 mg/kg bw i.v.) compared to the values before MP administration. Our findings suggest a physiological circadian rhythm of spontaneous and LPS-induced IL-1 production of monocytes, independent of physiological cortisol levels, whereas unphysiological amounts of endogenous and exogenous glucocorticoids cause a substantial inhibition of IL-1 production with a latency time of 8 hours.
Adult↗
Density-dependent tumor cell death and reversible cell cycle arrest: mutually exclusive modes of monocyte-mediated growth control.
The population development of five human tumor cell lines is examined under the influence of elutriator-prepared human monocytes in a serum-free hormone- and growth factor-supplemented medium. Analysis was performed by electronic counting and sizing of tumor cell nuclei and flow cytometric detection of cell cycle phases. Tumor cell death is triggered at rather low monocyte:tumor cell ratios (1:2 to 1:4) whereas it is strongly reduced at high monocyte densities. Furthermore, it is shown that confluence of the target cell population is a necessary prerequisite for lysis. The data suggest that in monocyte/tumor cell cocultures the decision on target cell lysis is not made by the effector cell, but rather by the target cell and that the criterion for this decision is the target cell's ability or inability to respond to a monocyte challenge by arresting the cell cycle in G1. Interactions between target cells play an important role in determining the result of this decision process. A common basis is suggested for this kind of density-dependent monocyte-triggered lysis and density-dependent cell death in 3T3 cell cultures as described previously.
Cell Cycle↗