Biomedical subjects

T Krakauer

Publications and source records attributed to T Krakauer.

At least 19 recordsLinked to original sources

PubMed1995

Differential inhibitory effects of interleukin-10, interleukin-4, and dexamethasone on staphylococcal enterotoxin-induced cytokine production and T cell activation.

The cytokine profile of human peripheral blood mononuclear cells (PBMC) stimulated by staphylococcal enterotoxin (SE) A and B was examined. Production of tumor necrosis factor (TNF alpha), interleukin (IL)-1, IL-6, IL-2, and gamma interferon (IFN-gamma) was observed. In contrast, Th2 cytokines IL-4 and IL-10 were absent from SEA- or SEB-stimulated PBMC. Moreover, adding IL-10 to SE-stimulated PBMC inhibited the production of IL-1, IL-6, TNF alpha, and IFN gamma by 50 to 80% but had less effect (8-30%) on T cell proliferation. IL-4 was less effective than IL-10 in inhibiting cytokine production and enhanced T cell proliferation by SEA or SEB. The anti-inflammatory agent, dexamethasone, was the most potent agent in controlling the SE-mediated effects as evidenced by inhibited T cell proliferation (55%) and reduced levels of IL-1, IL-6, and IFN gamma (60% to 100%) and TNF alpha (50%). Reducing levels of toxic mediators such as TNF alpha, IL-1, IL-6, and IFN gamma by dexamethasone in SE-induced T cell responses may be a useful therapeutic strategy to circumvent SE toxicity and pathogenesis.

Cytokines↗

PubMed1995

IL-10 inhibits the adhesion of leukocytic cells to IL-1-activated human endothelial cells.

Cytokines play an important role in the recruitment of leukocytes from blood to sites of tissue injury and inflammation. Previous studies showed that the pro-inflammatory cytokine, IL-1, induces the adhesion of leukocytes by up-regulating the expression of the adhesion molecules ICAM-1 and VCAM-1 on endothelial cells. IL-10, a pleiotropic mediator, inhibits the production of cytokines by macrophages and down-regulates the antigen-presenting function of macrophages, thereby acting as a suppressor of immune responses. This study was undertaken to evaluate the effect of IL-10 on the adhesion of leukocytic cells to human umbilical vein endothelial cells. IL-10 inhibited the adhesion of a human monocytic cell line (THP-1) and a human lymphoblastic T-cell line (MOLT-4) to IL-1-stimulated endothelial cells. IL-10 also down-regulated the expression of ICAM-1 and VCAM-1 on IL-1-activated endothelial cells. IL-10-treated THP-1 cells adhered less than untreated THP-1 cells to IL-1-activated endothelial cells, whereas direct treatment of MOLT-4 had minimal effect on its adhesion to cytokine-activated endothelial cells. These results suggest that IL-10 counteracts the pro-inflammatory effects of IL-1 and regulates the adhesion of leukocytic cells to endothelial cells.

Cell Adhesion↗

PubMed1995

Inhibition of toxic shock syndrome toxin-1-induced cytokine production and T cell activation by interleukin-10, interleukin-4, and dexamethasone.

Toxic shock syndrome toxin-1 (TSST-1) induced production of the cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1, IL-6, IL-2, and interferon-gamma (IFN-gamma) by human peripheral blood mononuclear cells (PBMC). In contrast, only low levels of IL-10 were present and IL-4 was absent in TSST-1-stimulated PBMC. Addition of IL-10 to TSST-1-stimulated PBMC inhibited the production of TNF-alpha, IL-1, IL-6, and IFN-gamma by 68%, 93%, 70%, and 86%, respectively, but had less effect (14%-37%) on T cell proliferation. IL-4 was less effective than IL-10 in inhibiting cytokine production and had no effect on T cell proliferation induced by TSST-1. Dexamethasone, an antiinflammatory agent, was the most potent agent in controlling TSST-1-mediated effects, as evidenced by inhibited T cell proliferation (> 74%), reduced levels of cytokines (70%-84%), and reduced expression of CD25 and CD69 on PBMC. Thus, dexamethasone may be a useful agent to mitigate TSST-1-mediated toxic shock.

Antigens, CD↗

PubMed1995

Levels of interleukin 6 and tumor necrosis factor in serum from humans vaccinated with live, attenuated Francisella tularensis.

The levels of interleukin 6 (IL-6) and tumor necrosis factor alpha in serum did not change significantly during the course of immunization with the live vaccine strain of Francisella tularensis. Higher levels of circulating IL-6 were found in the sera of vaccinees with good antibody responses than in the sera from nonresponders. Preimmunization levels of IL-6 in serum were also higher in responders than in nonresponders.

Adult↗

PubMed1995

Biological activity of toxic shock syndrome toxin 1 and a site-directed mutant, H135A, in a lipopolysaccharide-potentiated mouse lethality model.

A recombinant of toxic shock syndrome toxin 1 (TSST-1) which contains a single histidine-to-alanine mutation at residue 135 (H135A) was analyzed for toxicity and vaccine potential in a lipopolysaccharide (LPS)-potentiated mouse lethality model. The 50% lethal dose (LD50) of TSST-1 in BALB/c mice was 47.2 micrograms/kg, but H135A was not lethal when tested at a dose equivalent to 10 LD50s of TSST-1. Levels of tumor necrosis factor (TNF) and gamma interferon (IFN-gamma) in serum were, respectively, 10- and 50-fold higher in LPS-potentiated mice injected with 15 LD50s of TSST-1 than in mice given H135A. Mice injected with only TSST-1 did not have elevated levels of TNF or IFN-gamma in serum, while H135A plus LPS or LPS alone elicited identical, yet very low, levels of TNF and IFN-gamma. An enzyme-linked immunosorbent assay of H135A and TSST-1 with anti-TSST-1 serum yielded very similar dose-response curves, which strongly suggests that H135A serologically and conformationally resembles the native toxin. Mice immunized with H135A developed antibodies that recognized TSST-1 in an enzyme-linked immunosorbent assay and afforded protection against a 15-LD50 challenge of TSST-1 plus LPS. The pooled sera of mice immunized with either TSST-1 or H135A also prevented lymphocyte proliferation due to TSST-1.

Animals↗

PubMed1994

A sensitive ELISA for measuring the adhesion of leukocytic cells to human endothelial cells.

A new, sensitive ELISA using monoclonal antibodies reactive with surface molecules specific for various leukocytes was devised to measure the attachment of these cells to cultured monolayers of human umbilical vein endothelial cells. Preparations of peripheral blood mononuclear cells, a human monocytic cell line (THP-1) and a human lymphoblastic T cell line (MOLT-4) were used to test the sensitivity of this method and compare it with the conventional 51Cr-radiolabeled cell assay. The extent of adhesion to endothelial cells was assayed by measuring the optical density produced by a complex of peroxidase-labeled streptavidin, biotin-conjugated F(ab')2 anti-mouse Ig and monoclonal antibody on fixed leukocytic cells that had adhered to endothelial cells. This method is fast and sensitive, eliminates the use of radioisotopes, and, because the detection uses a specific marker on the cell of interest, can be used in preparations of unseparated mixtures of cells. As this is a microassay, using relatively small number of cells and reagents, the methodology can be applied to screen a large number of therapeutic agents that may regulate adhesion. Using this method, the anti-inflammatory corticosteroid, dexamethasone, was found to inhibit the adhesion of THP-1 and MOLT-4 cells to cytokine-activated endothelial cells.

Cell Adhesion↗

PubMed1994

Costimulatory receptors for the superantigen staphylococcal enterotoxin B on human vascular endothelial cells and T cells.

Cell-surface molecules on human vascular endothelial cells (ECs) and T lymphocytes that mediate staphylococcal enterotoxin B (SEB)-induced T cell proliferation and cytokine production were investigated. Expression of HLA-DR and intercellular adhesion molecule 1 (ICAM-1) on EC was induced by interferon-gamma (IFN-gamma). IFN-gamma-treated ECs bound SEB effectively and stimulated T cells to proliferate and secrete tumor necrosis factor alpha (TNF-alpha) and IFN-gamma. SEB-induced T cell proliferation was inhibited by monoclonal antibodies to CD2, CD11a, CD28, ICAM-1, and endothelial leukocyte adhesion molecule (ELAM). These antibodies also blocked production of the proinflammatory mediators, TNF-alpha and IFN-gamma, in SEB-stimulated T cell-EC cocultures. These results suggest that the surface molecules, CD11a:CD18/ICAM-1, CD2, CD28, and ELAM, are all important costimulatory receptors for T cell activation by superantigens with the EC as the antigen-presenting cell. Thus, like conventional antigens, multiple stimulatory signals from the interactions of these receptors are required for superantigen-induced immune responses with ECs and T cells. Reducing proinflammatory mediators such as TNF-alpha and IFN-gamma by these antibodies in SEB-induced T cell responses may be useful therapeutic strategy for circumventing SEB toxicity and pathogenesis.

Antigen-Presenting Cells↗

PubMed1994

Cell adhesion molecules are co-receptors for staphylococcal enterotoxin B-induced T-cell activation and cytokine production.

Enterotoxins produced by Staphylococcus aureus are potent mitogens for human T cells and cause lethal toxic shock. These superantigens bind to major histocompatibility complex class II on antigen-presenting cells outside the conventional peptide-binding groove and stimulate T cells expressing certain T-cell receptor V beta gene products. We investigated other cell-surface molecules on human peripheral blood mononuclear cells that can mediate staphylococcal enterotoxin B (SEB)-induced T-cell proliferation and cytokine production. SEB-induced proliferation of T cells was inhibited by monoclonal antibodies to CD2, CD11a, CD18, CD28, CD44, CD58 and ICAM-1. Anti-ICAM-1 also blocked the production of pro-inflammatory mediators, TNF alpha and IFN gamma by SEB-stimulated T cells. These data suggest that the surface molecules, CD11a:CD18/ICAM-1, CD2/CD58, CD28 and CD44, are all important co-receptors for T-cell activation by superantigens. Thus, like conventional antigens, multiple stimulatory signals from the interactions of these receptors are required for superantigen-induced immune responses. Reducing toxic mediators such as TNF alpha and IFN gamma by anti-ICAM antibodies in SEB-induced T-cell responses may be a useful therapeutic strategy to circumvent SEB toxicity and pathogenesis.

Antibodies, Monoclonal↗

PubMed1994

Serum levels of alpha and gamma interferons in hemorrhagic fever with renal syndrome.

Hemorrhagic fever with renal syndrome is an acute viral disease caused by Hantavirus. On the basis of clinical observation, the illness is divided into five sequential stages: febrile, hypotensive, oliguric, diuretic, and convalescent. Because interferons can be induced by viruses, and because their stimulating effects on immune cells can alter the course of viral infections, we examined the presence of alpha interferon (IFN-alpha) and gamma interferon (IFN-gamma) in 276 serum samples collected from 110 patients during the Korean Conflict. We tested these sera for IFN-alpha by bioassay with bovine kidney MDBK cells, and for IFN-gamma by a sandwich ELISA with antibodies specific for human IFN-gamma. We found variable, but persistently elevated levels of IFN-gamma throughout the various phases of the disease, which suggested persistent immune activation through convalescence. Moderate levels of IFN-alpha were found in all stages of infection.

Animals↗

PubMed1993

IL-1 and tumor necrosis factor-alpha each up-regulate both the expression of IFN-gamma receptors and enhance IFN-gamma-induced HLA-DR expression on human monocytes and a human monocytic cell line (THP-1).

Stimulation of human blood monocytes (adherent mononuclear cells) and the monocytic cell line, THP-1, by IL-1 or TNF-alpha leads to the up-regulation of IFN-gamma receptors. Scatchard analysis using 125I-IFN-gamma revealed a twofold increase in the number of IFN-gamma receptors on THP-1 cells without an alteration in the affinity of the receptor. The potential functional significance of this induction of IFN-gamma receptors on monocytes and THP-1 cells was investigated by examining the effect of IFN-gamma on MHC class II Ag expression by these cells. Both IL-1 and TNF-alpha enhanced the IFN-gamma-induced HLA-DR expression (> twofold) and this effect was inhibited by antibody to IFN-gamma. In the case of human monocytes, IL-1 or TNF-alpha, each by themselves also increased HLA-DR expression, which was also abrogated by antibody to IFN-gamma. The data suggest that the immunopotentiating effects of IL-1 and TNF-alpha are mediated in part by enhancing IFN-gamma receptor expression on monocytes and macrophages. This presumably would increase the capacity of IFN-gamma to activate macrophages, enabling them to express HLA-DR and present Ag more effectively.

HLA-DR Antigens↗

PubMed1993

A sensitive, specific immunobioassay for quantitation of human interleukin 6.

Picogram quantities of human interleukin 6 (h-IL-6) were detected by a two-step method. A microtiter plate coated with anti-h IL-6 monoclonal antibody was used to capture the IL-6 present in biological samples. An IL-6- dependent B cell line (7TD1) that proliferates in response to IL-6 was added to the captured IL-6. The lower limit of detection for this immunobioassay with serum or cell culture supernatants was 5 pg/ml. The specificity of the assay was achieved by the antibody used in the first step. The sensitivity was provided by the IL-6-dependent cell line. The method also allows for the removal of inhibitors, metabolites, antagonists or activating agents used to induce IL-6. This immunobioassay has the advantage over other current methods in that it measures immunoactive as well as biologically active IL-6.

Antibodies, Monoclonal↗

PubMed1993

Lipopolysaccharide inhibits the production of lymphocytic choriomeningitis virus in a human monocytic cell line.

The human monocytic cell line THP-1 was used as a model to study the mechanism of infection in the monocyte/macrophage, a natural target of lymphocytic choriomeningitis virus (LCMV) infection in vivo. Both the virulent strain, LCMV.WE, and the avirulent strain, LCMV.ARM, infected THP-1 cells, but did not stimulate THP-1 cells to secrete interleukin 1 (IL-1) or tumour necrosis factor (TNF-alpha). When lipopolysaccharide (LPS) was added to THP-1 cells together with LCMV, an 80 to 90% reduction in the number of infected cells (measured by immunofluorescence) and a 90% reduction in viral plaques was observed 5 to 6 days post-infection. Neither interferon alpha (IFN-alpha) nor IFN-beta were detected in supernatants from THP-1 cells after the addition of LCMV, LPS, or LPS plus LCMV. In contrast, the same levels of IL-1 and TNF-alpha were observed in the presence of LPS and LCMV, or LPS alone. However, antibodies to IL-1, TNF-alpha, interleukin 6 and IFN-alpha did not block the antiviral effect of LPS. In kinetic studies, LPS added 1 day after adding LCMV to THP-1 cells was still effective in reducing the number of infected cells. Our findings suggest that LPS alters cellular metabolism, possibly through the induction of IFN-alpha, and that IFN-alpha in the absence of LPS suppresses virus production.

Cytokines↗

PubMed1993

Toxicity of staphylococcal enterotoxins potentiated by lipopolysaccharide: major histocompatibility complex class II molecule dependency and cytokine release.

The biological effects of staphylococcal enterotoxins (SE), potentiated by bacterial lipopolysaccharide (LPS), were studied with mice. Control animals survived the maximum dose of either SE or LPS, while mice receiving both agents died. SEA was 43-fold more potent than SEB and 20-fold more potent than SEC1. The mechanism of toxicity was further examined with transgenic mice deficient in major histocompatibility complex class I or II expression. Class II-deficient mice were resistant to SEA or SEB. However, class I-deficient animals were less susceptible to SEA (30% lethality) than wild-type mice (93% lethality). In vitro stimulation of T cells from the three mouse phenotypes by SEA correlated well with toxicity. T cells from transgenic or wild-type mice were similarly responsive to SEA when presented by irradiated, wild-type mononuclear cells. These data confirmed that the toxicity of SE was mainly exerted through a mechanism dependent on the expression of major histocompatibility complex class II molecules. Toxicity was also linked to stimulated cytokine release. Levels in serum of tumor necrosis factor alpha, interleukin-6, and gamma interferon peaked 2 to 4 h after the potentiating dose of LPS but returned to normal within 10 h. Concentrations of interleukin-1 alpha were also maximal after 2 h but remained above the background for up to 22 h. Relative to the levels in mice given only SEA or LPS, the levels in serum of tumor necrosis factor alpha, interleukin-6, and gamma interferon increased 5-, 10-, and 15-fold, respectively, after injections of SEA plus LPS. There was only an additive effect of SEA and LPS on interleukin-1 alpha concentrations.

Animals↗

PubMed1992

Analysis of the heterogeneity of the biological responses to native and mutant human interleukin-6.

The structure-function relationships of the biological activities of mutant varieties of the pleiotropic cytokine interleukin-6 (human) were measured by three assays: induction of immunoglobulin M (IgM) secretion from an Epstein-Barr virus-transformed human B cell line and induction of fibrinogen secretion from either a human hepatoma cell line or a rat hepatoma cell line. The biological effects of the cytokine were characterized by three parameters as determined by a novel analysis: effectiveness (the maximal response attainable), efficiency (the concentration yielding a half-maximal response), and complexity (a measure of heterogeneity and feedback control). Substitution of serine for cysteine was associated with a reduction in the effectiveness of interleukin-6 in both fibrinogen secretion assays. In the assay with human hepatoma cells, there was also a profound reduction in efficiency. Serine substitution in the human IgM synthesis assay appears mainly to reduce the efficiency. Deletion of amino acids 4 to 23 increased the efficiency in the rat hepatoma assay. The complexity parameter suggests the presence of multiple receptor classes or negative feedback in all three assays. Use of the proposed sequential approach to the analysis of dose-response relations in bioassays provides a more useful quantitative assessment of activities as well as more insight into the complexity of the reactions.

Animals↗

PubMed1991

A method for the quantitative analysis and standardization of interleukin-1 bioactivity.

A method is presented for the reproducible quantitation of the biological activity of interleukin 1 (IL-1). This method provides diagnostic tools which give insights into the qualitative aspects of the binding of IL-1 and of the resulting activation of the responder thymocytes; for example, whether the lymphokine and/or the responder population is heterogeneous, or whether a threshold level exists. It establishes under what circumstances the assumptions on which it is based are reasonably adhered to and, consequently, quantitative estimation in the manner it prescribes is justified. It also gives a simple way to calculate both the maximal response attainable for each preparation in an assay and the dilution of a particular preparation that would produce a half-maximal response, the accepted unit of activity of IL-1. This empirical technique provides an improved means of comparing the activities of various preparations of IL-1 in bioassays using various stocks of responder cells and reagents. It should also be applicable to the evaluation of the biological activity of lymphokines in general.

Animals↗

PubMed1991

Immuno-enhancing effects of ricin.

The effect of ricin on human peripheral blood mononuclear cells (PBMC) was tested in vitro. At low concentrations (10(-3) and 10(-4) micrograms/ml), ricin potentiated the effect of lipopolysaccharide to induce interleukin 1 (IL-1). Ricin was not mitogenic or co-mitogenic with phytohaemagglutinin or concanavalin A in PBMC cultures at low concentrations (less than 10(-4) micrograms/ml). Higher concentrations of ricin (greater than 10(-3) micrograms/ml) inhibited production of IL-1 by PBMC and the mitogen-driven proliferation of PBMC cultures.

Adjuvants, Immunologic↗

PubMed1986

Human interleukin 1.

Interleukin 1 (IL-1), a product of stimulated monocytes or macrophages, is defined by its ability to enhance the response of thymocyte to mitogenic stimulation. Numerous studies attribute a multiplicity of other biological functions to IL-1 in immunological and inflammatory reactions. IL-1 also appears to be identical with endogenous pyrogen. Even though this mediator is produced in minute quantities and is active at very low concentrations, greatly complicating its purification, knowledge of its chemical structure and biochemical properties is rapidly increasing. The activity of human IL-1 is associated with multiple molecules of similar size, but subtly different compositions. Structure-function relations, most particularly the question of whether the functional diversity of IL-1 is a reflection of structural diversity or simply of diversity of target-cell responses to a single molecule can now be addressed, as the IL-1 components have been purified to homogeneity, on the one hand, and a precursor molecule, derived from a cloned cDNA sequence, has been obtained.

Animals↗

PubMed1985

Biochemical characterization of interleukin 1 from a human monocytic cell line.

A protein with interleukin 1 (IL-1) activity was obtained from the human acute monocytic leukemia cell line (THP-1) and purified by ultrafiltration, Ultrogel AcA54 chromatography, isoelectric focusing, and discontinuous polyacrylamide gel electrophoresis. Like the pI 6.8 species of IL-1 from human peripheral blood monocytes (PBM), the cell line IL-1 has a molecular weight (MW) of 14,000, a pI of 6.8, is heat labile, and does not bind to concanavalin A-Sepharose. Chemical modification of arginine residues by phenylglyoxal or sulfhydryl groups by N-ethyl maleimide and iodoacetamide completely destroys the activity of IL-1 from THP-1 cells as well as that of the pI 6.8 component from PBM. In contrast, the pI 5.1 component of PBM IL-1 is resistant to heat denaturation and sulfhydryl reagents, although it is totally inactivated by phenylglyoxal. IL-1 from THP-1 cells enhanced the proliferative response of the same subpopulations of PNA- thymocytes as IL-1 from PBM. These observations suggest that IL-1 derived from this cell line is similar to the IL-1 pI 6.8 species produced by human monocytes, and distinct from the pI 5.1 species.

Biological Assay↗