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H Loppnow

Publications and source records attributed to H Loppnow.

At least 55 records · Page 3Linked to original sources
PubMed1992

FcR+ and FcR- monocytes differentially secrete monokines during pokeweed mitogen-induced T-cell-monocyte interactions.

Monocyte subpopulations which differ in the expression of Fc receptor for human IgG (FcRI) differentially regulate the T-cell-dependent, pokeweed mitogen (PWM)-induced, polyclonal B-cell response. We, thus, studied the cytokine production in human peripheral blood monocyte and T-lymphocyte cultures activated with this lectin. Monocytes or their FcR+ and FcR- subpopulations stimulated with PWM were cultured with or without T lymphocytes or their CD4+ and CD8+ subsets. Both monocyte subpopulations cultured alone produced similar amounts of tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), but FcR- monocytes showed significantly enhanced ability to secrete interleukin-1 (IL-1). T cells, especially CD4+, added to monocyte cultures enhanced IL-1 production. This enhancement was presumably due to interferon-gamma (IFN-gamma) release by T lymphocytes, since this lymphokine enhanced IL-1 secretion when added to PWM-stimulated cultures of monocytes. Addition of monocytes, in particular the FcR+ subpopulation, greatly enhanced production of IFN-gamma by T lymphocytes. Although both T-cell subsets produced IFN-gamma, the CD4+ cells were more efficient. These results indicate that in PWM-stimulated cultures subpopulations of monocytes differ in secretion of cytokines, which might explain their differential effect on T-cell-dependent immune responses in vitro.

Antigens, Differentiation↗
PubMed1991

Hyperplasia of somatostatin and pancreatic polypeptide immunoreactive cells in dogs with idiopathic atrophy of the exocrine pancreas.

The pancreatic tissue from 25 dogs with idiopathic atrophy of the exocrine pancreas, and from 6 control dogs, was studied histologically and immunohistometrically. Cells producing insulin (B), glucagon (A), somatostatin (D), and pancreatic polypeptide (PP) were identified using specific antisera and the ABC technique. Histometrical quantitation revealed differences in the distribution of these cell types between the right and left pancreatic lobe. Initial stages of atrophy showed little changes concerning the relative proportions of the four cell types examined. In more advanced stages of atrophy, however, there was significant increase in the percentage of the D cells in the cell population of the left lobe. B and A cells showed no significant changes. In final stages, only tiny tissue spots were considered a secondary and regenerative phenomenon, but an endocrine dysregulation cannot be excluded. Atrophy accompanied by diabetes mellitus and a lack of B cells seem to be due to a deficiency of insulin.

Animals↗
PubMed1991

Bacterial endotoxin: molecular relationships between structure and activity.

The significance of endotoxins in bacterial infection and their role as bacterial surface antigens (O antigens) have stimulated investigations into their chemical nature and the mechanisms of their biologic action during the last few decades. This article summarizes some of the recent results and emphasizes structure-activity relationships.

Animals↗
PubMed1991

Interleukin-1 gene expression in rabbit vascular tissue in vivo.

Cultured human vascular endothelial and smooth muscle cells express interleukin-1 (IL-1) genes when exposed to bacterial lipopolysaccharides (LPS) and a variety of inflammatory mediators. Local production of IL-1 may contribute to the pathogenesis of various vascular diseases. Therefore the ability of intact vascular tissue to accumulate IL-1 mRNA and synthesize de novo biologically active IL-1 protein was examined. Escherichia coli LPS (10 micrograms/kg) was administered intravenously to adult rabbits and total RNA was isolated from aortic tissue at various times after LPS injection. In saline-injected rabbits, RNA extracted from the thoracic aorta contained little or no IL-1 message detected by Northern analysis using IL-1 alpha and beta cDNA probes cloned from an LPS-stimulated rabbit splenic macrophage library. Lipopolysaccharide treatment promptly induced transient accumulation of mRNA for IL-1 alpha and IL-1 beta within the aorta (maximal 1-hour after injection). Short-term organoid cultures of rabbit aorta exposed to LPS in vitro synthesized immunoprecipitable IL-1 alpha protein. Extracts of aortic tissue excised 1.5 to 3.0 hours after intravenous LPS administration contained immunoreactive and biologically active IL-1 alpha. Anti-rabbit IL-1 alpha antibody neutralized the biologic activity (more than 90%). Microscopic and immunohistochemical studies did not disclose adherent or infiltrating macrophages in rabbit aorta at the time of maximal IL-1 mRNA accumulation after LPS administration (1.5 hours), indicating that intrinsic vascular wall cells rather than mononuclear phagocytes probably account for the IL-1 activity induced by LPS. In addition, aortic tissue from rabbits fed an atherogenic diet showed an enhanced ability to accumulate IL-1 alpha and beta mRNA and produce immunodetectable protein in response to LPS administration. These studies demonstrate inducible IL-1 gene expression in rabbit vascular tissue in vivo and support a local role for this cytokine in vascular pathophysiology.

Animals↗
PubMed1990

Lipid A, the immunostimulatory principle of lipopolysaccharides?

Lipid A has been found to be an inducer of IL-1 with similar potency as LPS. Partial structures of lipid A or core oligosaccharides are less active or not active at all. We propose that lipid A is the structure responsible for induction of immunostimulatory or immunoregulatory properties of LPS.

Adjuvants, Immunologic↗
PubMed1990

Cytokine induction by lipopolysaccharide (LPS) corresponds to lethal toxicity and is inhibited by nontoxic Rhodobacter capsulatus LPS.

Many pathological effects of gram-negative bacteria are produced by their cell wall-derived lipopolysaccharides (LPSs). Differing pathogenicity of gram-negative LPSs, however, may depend on their capacities to induce cytokines. Thus, we studied the lethal toxicity of four nonenterobacterial LPSs and compared it with their capacity to induce mononuclear cell (MNC)-derived interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF). Unstimulated MNC did not release these cytokines. LPS from the phototrophic strain Rhodobacter capsulatus 37b4 elaborated little toxicity in galactosamine-treated mice (10 micrograms of LPS per mouse was the 100% lethal dose [LD100]) and induced IL-1 and IL-6 release only at high concentrations (10 to 50 micrograms of LPS per ml). R. capsulatus LPS failed to induce TNF activity even at the highest concentration tested (100 micrograms of LPS per ml). In contrast, LPS derived from Pseudomonas diminuta NCTC 8545 or the nodulating species Bradyrhizobium lupini DSM 30140 and Rhizobium meliloti 10406 expressed lethal toxicity (LD100, 1,000, 100, and 10 ng per mouse, respectively) and induced IL-1 or IL-6 (10 to 100, 10, and 1 ng of LPS per ml, respectively) at concentrations 1,000- to 10,000-fold lower than effective levels of R. capsulatus LPS. LPSs from P. diminuta, B. lupini, and R. meliloti also stimulated TNF production and release. MNC accumulated cell-associated IL-1 activities under circumstances in which released activity was readily detected. The cells contained only scant IL-6 activity, indicating release of this mediator rather than intracellular accumulation. Antisera to the respective cytokines inactivated biological activities of the samples selectively. The R. capsulatus LPS inhibited cytokine induction by LPS from P. diminuta, B. lupini, and R. meliloti in coincubation experiments. These results show that the in vivo lethality of the LPSs tested correlates with the induction of monocyte-derived cytokines in vitro. The results of this study suggest that the different lethality of various LPSs from gram-negative bacteria may be due to the differential ability of these LPSs to induce cytokine production.

Animals↗
PubMed1990

Proliferating or interleukin 1-activated human vascular smooth muscle cells secrete copious interleukin 6.

The cells that make up blood vessel walls appear to participate actively in local immune and inflammatory responses, as well as in certain vascular diseases. We tested here whether smooth muscle cells (SMC) can produce the important inflammatory mediator IL6. Unstimulated SMC in vitro elaborated 5 X 10(3) pg recIL6/24h (i.e., biological activity equivalent to 5 X 10(3) pg recombinant IL6 (recIL6), as determined in B9-assay with a recIL6 standard). Several pathophysiologically relevant factors augmented IL6 release from SMC including 10 micrograms LPS/ml (10(4) pg recIL6), 10 ng tumor necrosis factor/ml (4 X 10(4) pg recIL6), and most notably 10 ng IL1/ml (greater than or equal to 3.2 X 10(5) pg recIL6). Production of IL6 activity corresponded to IL6 mRNA accumulation and de novo synthesis. SMC released newly synthesized IL6 rapidly, as little metabolically labeled material remained cell-associated. In supernatants of IL1-stimulated SMC, IL6 accounted for as much as 4% of the secreted proteins. In normal vessels SMC seldom divide, but SMC proliferation can occur in hypertension or during atherogenesis. We therefore tested the relationship between IL6 production and SMC proliferation in response to platelet-derived growth factor (PDGF) in vitro. Quiescent SMC released scant IL6 activity, whereas PDGF (1-100 ng/ml) produced concentration-dependent and coordinate enhancement of SMC proliferation and IL6 release (linear regression of growth vs. IL6 release yielded r greater than 0.9). IL6 itself neither stimulated nor inhibited SMC growth or IL6 production. Intact medial strips studied in short-term organoid culture produced large quantities of IL6, similar to the results obtained with cultured SMC. These findings illustrate a new function of vascular SMC by which these cells might participate in local immunoregulation and in the pathogenesis of various important vascular diseases as well as in inflammatory responses generally.

Cell Division↗
PubMed1989

IL-1 induction-capacity of defined lipopolysaccharide partial structures.

Natural and synthetic lipid A as well as natural and synthetic oligosaccharide partial structures of LPS were examined in dose-response experiments to define the minimal structure necessary for IL-1 induction and release in cultures of human mononuclear cells. Wild type LPS (S. abortus equi) and rough mutant LPS was active in minimal-doses of 1 to 100 pg/ml, whereas synthetic heptaacyl and hexaacyl lipid A (Salmonella minnesota and Escherichia coli lipid A, respectively) induced IL-1 in minimal-doses of 100 to 1,000 pg/ml and 10 to 1,000 pg/ml, respectively. Nanogram amounts (0.1 to 10 ng/ml) of synthetic monodephospho partial structures of E. coli lipid A were necessary for IL-1 induction. Synthetic pentaacyl partial structures induced IL-1 very weakly. Synthetic tetraacyl and bisacyl partial structures lacking non-hydroxylated fatty acids were not active. Compared to LPS million-fold higher doses of natural and synthetic 3-deoxy-D-manno-octulosonic acid containing core oligosaccharides were necessary for IL-1 induction. Dose-response investigations with LPS and natural or synthetic partial structures established the following hierarchy in IL-1 induction-capacity: LPS greater than lipid A much greater than lipid A partial structures greater than core oligosaccharides greater than oligoacyl lipid A. Lipid A was shown here to be the portion of LPS mainly responsible for induction of IL-1 activity. The high potency of lipid A in inducing IL-1 release and the failure of the precursor Ia of lipid A to induce IL-1 production and release was also observed measuring intracellular IL-1 activity after freeze-thawing the cells. Levels of IL-1 beta mRNA in extracts of mononuclear cells correlated with biologic activity. In co-incubation experiments, precursor Ia of lipid A produced dose-dependent inhibition of production and release of IL-1 activity induced by lipid A or LPS, but not by Staphylococcus epidermidis or PHA. Incubation of cells with precursor Ia for 1h, followed by a medium change and further incubation of stimulus without precursor Ia of lipid A also resulted in inhibition. We conclude that lipid A is the main portion of LPS responsible for induction of IL-1, and that specific activation- and/or binding-mechanisms are involved in stimulation of cells with LPS and/or lipid A.

Acinetobacter↗
PubMed1989

Adult human vascular endothelial cells express the IL6 gene differentially in response to LPS or IL1.

We investigated the regulation of IL6 biological activity, de novo synthesis, and mRNA levels in adult vascular endothelial cells (EC) by bacterial endotoxin or inflammatory cytokines. Cells incubated without stimulus released scant IL6 activity. IFN gamma, IL2, or PDGF did not augment IL6 release from EC. LPS, lipid A, and TNF increased IL6 release modestly (5 to 20-fold), while recombinant IL1s (rIL1s) stimulated this process 100 to 400-fold. Differential release of IL6 from EC treated with LPS or rIL1 continued for at least 144 hr. Exposure to LPS or rIL1 caused EC to synthesize IL6 de novo. EC secreted the newly synthesized IL6 into the supernatant, rather than retaining it within or bound to cells. EC accumulated IL6 mRNA after 3 hr of exposure to rIL1. However, we could only detect IL6 message in cells incubated with LPS under "superinduction" conditions with cycloheximide, consistent with lower levels of IL6 biological activity in response to LPS compared to IL1 stimulation. We propose that local production of IL6 by vascular EC, which comprise the barrier between tissues and the blood, may influence regional immune and inflammatory responses.

Antigen-Antibody Reactions↗
PubMed1989

Detection of interleukin 1 with human dermal fibroblasts.

A fibroblast proliferation assay was developed for the detection of interleukin 1 (IL 1). Proliferation was measured by thymidine incorporation and by staining of cellular proteins with crystal violet. Response of fibroblasts was optimal at cell numbers of 4,000 to 9,000 cells/culture and an incubation period of four days. Serum content of the culture medium, ranging from 1 to 10% fetal calf serum (FCS), enhanced the proliferative response in a concentration-dependent manner, while higher concentrations of FCS did not lead to further increase. Both detection methods were equally suitable for the measurement of IL 1 biological activity in purified and crude preparations. In contrast to the conventional thymocyte comitogenic assay, the fibroblasts in this assay did not proliferate in response to IL 2 or IL 6. Fibroblasts were weakly stimulated by recombinant (rec) tumor necrosis factor (rec TNF-alpha); they did, however, not proliferate in response to mitogens, lipopolysaccharide, rec granulocyte-macrophage colony stimulating factor (rec GM-CSF), macrophage-CSF, rec interferon-gamma, insulin or transferrin. The detection of IL 1 activity by crystal violet staining of human dermal fibroblasts was easier and faster than by measurement of thymidine incorporation of fibroblasts or mouse thymocytes; without loss of sensitivity, the sample capacity of the IL 1 assay could be enhanced, and the use of experimental animals was avoided.

Cell Count↗
PubMed1989

Characterization of a platelet derived factor modulating phagocyte functions and cooperating with interleukin 1.

During experiments aiming at the generation of monoclonal antibodies against native human interleukin 2 an antibody of different specificity was obtained, recognizing a polypeptide contaminant within the antigen preparation used for immunization. This antigen was shown to represent a release protein from human blood platelets. Amino acid sequence analysis of the immunopurified antigen revealed its identity as beta-thromboglobulin antigen. Depending on the source of antigen (freshly lysed platelets, platelet containing cell culture supernatants) various forms of the polypeptide, differing in the degree of N-terminal truncation, were found. Beta-thromboglobulin antigen preparations differing in peptide composition also had different capacities for modulating spontaneous as well as Fc-receptor dependent chemiluminescence of human monocytes and granulocytes. In contrast to former reports, no mitogenic activity for human dermal fibroblasts was found with beta-TG antigen (CTAP III) alone, but only in combination with human interleukin 1 and heparin, the three molecules acting synergistically. These findings indicate that beta-TG antigen could play a functional role in linking the blood clotting system to the immune system.

Antibodies, Monoclonal↗
PubMed1989

Interleukin 1 and tumor necrosis factor: studies on the induction by lipopolysaccharide partial structures.

Minimal concentration ranges of lipopolysaccharides, natural and synthetic lipid As, and partial structures were established for the induction of release of IL-1 and TNF from human MNC. LPS was more potent than lipid A. Partial structures of lipid A lacking nonhydroxylated fatty acids were inactive, but in combination with LPS or lipid A exhibited time-dependent synergistic or antagonistic effects.

Glycolipids↗
PubMed1989

Comparative analysis of cytokine induction in human vascular endothelial and smooth muscle cells.

Cells of the blood vessel wall are both targets for and sources of certain cytokines. Various stimuli including bacterial lipopolysaccharides (LPS) or Interleukin 1 (IL1) induce elaboration of immunoregulatory and inflammatory mediators by human vascular endothelial cells (EC) and smooth muscle cells (SMC). We compared the capacity of EC and SMC to produce interleukin 6 (IL6) in response to LPS or its lipid A moiety. Cultured SMC release IL6 even without addition of stimuli, this basal IL6 secretion increased 2 to 4 fold in response to LPS. In contrast, unstimulated EC released little IL6, but exposure to LPS increased IL6 elaboration approximately 10 fold. Lipid A also augmented IL6 production by both EC and SMC. Radioimmunoprecipitation experiments compared de novo IL6 synthesis by EC and SMC in response to LPS, and yielded results consistent with the studies of biological activity. Unstimulated EC produced no precipitable IL6, LPS-stimulated EC released newly synthesized IL6, although to a lesser extent than did IL1-stimulated cells. SMC secreted precipitable IL6 without added stimulus and in increasing amounts following exposure to LPS or IL1. Thus EC and SMC exhibit substantial quantitative differences in IL6 synthesis and release, basally and in response to LPS. The capacity of these intrinsic vessel wall cells to secrete this important immunomodulator might contribute to local regulation of the immune or inflammatory responses.

Cells, Cultured↗
PubMed1988

Stimulation of human and murine adherent cells by bacterial lipoprotein and synthetic lipopeptide analogues.

Lipoprotein from the outer membrane of Escherichia coli and its synthetically prepared N-terminal lipopeptide segments Pam3Cys-Ser-Ser-Asn-Ala and Pam3Cys-Ser, as well as lipoprotein from other Enterobacteriaceae, constitute potent polyclonal B lymphocyte activators. Here, we demonstrate that these compounds were also able to stimulate human and murine leukocytes: in murine macrophages, we could show the induction of interleukin 1 release by the mitogens, as measured in the thymocyte proliferation assay. Moreover, murine peritoneal exudate cells were stimulated to secrete prostaglandins E2 (PGE2) and F2 alpha (PGF2 alpha). The effect of Pam3Cys-Ser on the murine macrophage cell line P388D1 was also tested: the compound induced an increase in proliferation, as measured by a thymidine incorporation assay. In addition, the cell line could be induced to release IL 1 into the supernatant. Correspondingly, induction of IL 1 release could also be demonstrated in human mononuclear cells. Our results demonstrate that the two novel synthetic lipopeptides are potent stimulators for human monocytes and murine macrophages. These findings may be important for the elucidation of the role of these bacterial surface components in the course of bacterial infections.

Animals↗
PubMed1986

Induction of human interleukin 1 by bacterial and synthetic lipid A.

Lipopolysaccharides (LPS) are well known inducers of interleukin 1 (IL 1). Here we show that synthetic heptaacyl Salmonella minnesota (compound 516) and synthetic E. coli type (compound 506) lipid A, as well as monodephospho part structures thereof, are able to induce IL 1 production in human mononuclear cells. The 4'-monodephospho part structure (compound 505) was found to be the most active IL 1 inducer as compared to compound 506 and the 1-monodephospho part structure (compound 504). Synthetic lipid A precursor Ia, lacking nonhydroxylated fatty acids (compound 406), and its 1- or 4'-monodephospho part structures (compounds 404 and 405) did not induce IL 1 production. IL 2 is not produced during stimulation with the synthetic compounds. IL 1 activity was partially heat labile and could be inhibited by a rabbit antiserum against human leukocytic pyrogen. These results show that the lipid A component of LPS is active in inducing IL 1 and that the presence of 3-acyloxyacyl residues is necessary for IL 1 induction.

Blood Physiological Phenomena↗