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Biomedical subjects

H D Volk

Publications and source records attributed to H D Volk.

At least 19 recordsLinked to original sources
PubMed1995

Mechanism of endotoxin desensitization: involvement of interleukin 10 and transforming growth factor beta.

Tolerance of monocytes/macrophages to endotoxin (lipopolysaccharide [LPS]) can be induced both in vivo and in vitro by LPS itself. Exposure to LPS, even at a very low dose, induces a downregulation of cytokine response to a second high dose LPS challenge. To learn more about the unknown mechanisms of this phenomenon, we studied the role of antiinflammatory cytokines in this process. Preculture of human peripheral blood monocytes for 24 hours with low concentrations of LPS induced hyporesponsiveness to high-dose LPS rechallenge with respect to tumor necrosis factor (TNF) alpha and interleukin (IL) 10 but not IL-1RA production. These results suggest that LPS tolerance reflects a functional switch of monocytes rather than a general LPS hyporesponsiveness. IL-10 and transforming growth factor (TGF) beta 1 showed additive effects in replacing LPS for induction of LPS hyporesponsiveness in vitro. Additionally, neutralizing anti-IL-10 and anti-TGF-beta monoclonal antibodies prevented induction of LPS tolerance. In vitro induced LPS tolerance looks like the ex vivo LPS hyporesponsiveness of monocytes from septic patients with fatal outcome: downregulation of LPS-induced TNF-alpha and IL-10 production but not of IL-1RA secretion. LPS hyporesponsiveness in septic patients was preceded by expression of IL-10 at both the mRNA and protein level. In summary, our data suggests that IL-10 and TGF-beta mediate the phenomenon of LPS tolerance in vitro and perhaps in vivo (septic patients), too.

Cells, Cultured↗
PubMed1995

Effect of granulocyte colony-stimulating factor treatment on ex vivo blood cytokine response in human volunteers.

We explored the ex vivo alteration in the cytokine release of stimulated blood taken from healthy volunteers treated subcutaneously with 480 micrograms granulocyte colony-stimulating factor (G-CSF). In a double-blind, controlled, randomized study with 21 volunteers who received G-CSF once or twice 24 hours apart, we measured lipopolysaccharide (LPS)-inducible release of various cytokines and soluble receptors at different times after treatment. At day 1 after a single dose of G-CSF, mediator release was also initiated with muramyl dipeptide, Staphylococcus aureus enterotoxin A, lipoteichoic acid, streptolysin O, complement factor C5a, phytohemagglutinin, or phorbol myristate acetate. In blood from G-CSF-treated subjects, our major findings were (1) a maximal 12-fold increase in interleukin-1 receptor antagonist (IL-1ra) release and an increase of both the p55 and p75 soluble tumor necrosis factor (TNF) receptors; (2) a reduction in TNF release when using all the various stimuli described except LPS; (3) an increase in G-CSF and, to lesser extent, in IL-6, IL-8, and IL-10 release; and (4) an attenuation of interferon-gamma (IFN-gamma) and granulocyte-macrophage (GM)-CSF release. Our findings demonstrate that the major effect of G-CSF treatment is a change in the responsiveness of blood towards a variety of stimuli, which we interpret as a shift toward an antiinflammatory cytokine response.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1995

Lipopolysaccharide-induced interleukin-10 in mice: role of endogenous tumor necrosis factor-alpha.

Interleukin (IL)-10 is known to protect mice against the lethal effects of lipopolysaccharides (LPS) and is considered to be an anti-inflammatory cytokine which suppresses the production of pro-inflammatory cytokines. We have examined the interactions of the pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) with IL-10. Neutralization of TNF-alpha in murine bone marrow-derived macrophages resulted in a significant reduction of LPS-inducible IL-10 production. In mice, injection of 5 mg/kg LPS induced circulating IL-10 with a biphasic time course exhibiting an early peak 1.5 h after challenge (synchronous with TNF-alpha) and, after a nadir at 6 h, a second increase between 8 and 12 h. Treatment of mice with neutralizing anti-mouse TNF-alpha antiserum significantly increased LPS-induced IL-10 plasma levels between 1.5 and 6 h but diminished those at 12 h, while circulating IL-6, interferon-gamma (IFN-gamma) and granulocyte colony-stimulating factor (G-CSF) concentrations were attenuated overall, without a biphasic response. Analysis of LPS-induced IL-10 mRNA expression in different tissues 1 h and 8 h after LPS or LPS plus anti-TNF-alpha revealed that the amount of transcripts in the liver correlated with circulating early and late IL-10 levels. Our findings suggest that endogenous TNF-alpha down-regulates the early and up-regulates the late LPS-induced IL-10 synthesis in vivo and that the liver is the major source of circulating IL-10 after stimulation with LPS.

Animals↗
PubMed1995

Up-regulation of monocytic IL-10 by tumor necrosis factor-alpha and cAMP elevating drugs.

It is well established that endotoxin [lipopolysacharide (LPS)] induces pro-inflammatory cytokine production in monocytes, which is followed by secretion of the anti-inflammatory cytokine, IL-10. IL-10 down-regulates inflammatory response [tumor necrosis factor (TNF)-alpha, IL-1, IL-6, IL-8] as well as IL-10 synthesis itself. We wondered whether pro-inflammatory cytokines such as TNF-alpha may be involved in the regulation of human IL-10 synthesis. TNF-alpha induced de novo IL-10 mRNA expression in a dose-dependent manner but no IL-10 protein in human peripheral blood mononuclear cells. Furthermore, LPS-induced IL-10 gene and protein expression was significantly inhibited by neutralizing anti-TNF-alpha mAb. On the basis of these results, we conclude that TNF-alpha is involved in the up-regulation of its antagonist IL-10. Paradoxically, drugs that effectively inhibit expression of TNF-alpha via the elevation of intracellular cAMP level (iloprost, pentoxifylline, prostaglandin E2 and N6,2-O-dibutyryl cAMP) augmented the endotoxin-induced IL-10 synthesis at both protein and mRNA levels. In order to provide a basis for the analysis of the transcriptional regulation of the human IL-10 gene, we isolated a fragment of the human IL-10 gene containing 1308 bp of the 5' non-coding sequence. It shows remarkable homology to the mouse IL-10 promoter in regions that have been associated with transcriptional regulation, including a cAMP responsive element which could explain the cAMP-mediated effects. The lack of a NF-kappa B-like binding site in the human sequence suggests a NF-kappa B-independent mechanism of TNF-alpha-induced IL-10 gene activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Immunodepression following neurosurgical procedures.

OBJECTIVE: To determine the influence of a selective, sterile central nervous system surgery on immune reactivity, particularly whether a decrease of monocytic human leukocyte antigen-DR expression, indicating immunodepression, occurs after neurosurgery and if this measurement is useful for identification of patients with a high risk of infection. DESIGN: Prospective study. SETTING: Department of neurosurgery and intensive care unit in a university hospital. PATIENTS AND INTERVENTIONS: Blood samples were obtained from 46 patients at least once during the first 3 days after undergoing sterile central nervous system surgery. Fourteen of these patients developed infectious complications as defined by clinical and microbiological criteria. In ten of 46 patients, paired samples of blood and cerebrospinal fluid were collected from a ventricle drain at the following times: 1 day before surgery; several times on the day of surgery; and every day after surgery for at least 6 days. MEASUREMENTS AND MAIN RESULTS: Monocytic human leukocyte antigen-DR expression, as measured by flow cytometry on days 1 through 3 after surgery in 46 patients, was lower in 14 patients who developed infection after neurosurgery (p < .0001). In all ten closely monitored patients, monocytic human leukocyte antigen-DR expression decreased temporarily after surgery. Of these patients, only one patient showed a persistent and considerably decreased monocytic human leukocyte antigen-DR expression. This patient was the only patient in this subgroup who developed sepsis syndrome. In order to assess whether the monocytic human leukocyte antigen-DR decrease was associated with a preceding inflammatory response, local and systemic concentrations of interleukin (IL)-1 beta, IL-6, IL-8, tumor necrosis factor-alpha, and interferon-gamma were measured in this subgroup. These cytokines were not detectable in plasma during the first days after surgery. In contrast, considerable increases of IL-6 and IL-8 concentrations were detectable in cerebrospinal fluid within hours after surgery. CONCLUSIONS: A decrease of monocytic human leukocyte antigen-DR expression occurs after neurosurgery and is associated with a preceding, strong, intracranial (but not systemic) inflammatory response. A very low monocytic human leukocyte antigen-DR expression (< 30% positive monocytes) suggests the possibility of infection. Measurement of monocytic human leukocyte antigen-DR expression could help to detect patients with a high risk of infection after neurosurgery. Our results suggest that even sterile central nervous system surgery may contribute to general immunodepression. The local intracranial inflammatory response may be involved in this process.

Adult↗
PubMed1994

A novel multispecific competitor fragment for quantitative PCR analysis of cytokine gene expression in rats.

Competitive polymerase chain reaction (PCR) is a sensitive method for quantification of cytokine mRNA expression. Co-amplification of an internal standard serves as control for comparing the efficiency of PCR in different samples. We have developed a novel control fragment for multiple analyses of rat cytokine gene expression containing primers for IL-1 beta, IL-2, IL-4, IL-5, IL-6, IL-10, TNF-alpha, TGF-beta 1, IFN-gamma and MIP-2. Additional primers were incorporated to analyse the content of T cells (CD3), activated T cells (CD25) and housekeeping genes (beta-actin and HPRT). As an example we demonstrate analysis of IL-2 mRNA expression in small pieces of kidney tissue obtained from rats after kidney allotransplantation. The IL-2 expression decreased tenfold during treatment with an anti-rat CD4 monoclonal antibody as compared to untreated animals.

Animals↗
PubMed1994

Late acute rejection in long-term renal allograft recipients. Diagnostic and predictive value of circulating activated T cells.

Episodes of acute rejection can occur in functional renal grafts even at a very late stage after transplantation. They are not necessarily due to patient noncompliance. The incidence of late acute rejection is commonly underestimated because the diagnosis generally requires histopathology in order to rule out other origins of declining graft function, even more so, as the typical signs of acute rejection as seen in the early posttransplantation period (sudden and rapid increase of creatinine serum level, inflammatory signs) are missing. Histology revealed acute rejection in 157 of 412 renal allograft recipients suffering from progressive graft deterioration between the 2nd and 18th year after Tx. Late acute rejection was clearly associated with elevated levels of activated HLA-DR+ T cells in the peripheral blood. These cells were characterized by flow cytometry to be postmitotic activated effector-T cells belonging to the CD4+ and CD8+ "memory" T cell pool. The high sensitivity (97%) and specificity (88%) of flow cytometric analysis allows for the discrimination between late acute rejection and other causes of deteriorating graft function (infection, toxicity, arteriopathy, chronic rejection). Additionally, this immune monitoring can predict the success of antirejection therapy as early as a few days after initiation of treatment while conventional parameters do not reflect the therapeutic result until 1-3 weeks later. In addition to this, peripheral T cell activation also seems to identify a subgroup of patients with chronic rejection who would respond, at least partially, to steroid bolus therapy. As a result, this parameter is very useful for the clinical management of patients suffering from late deterioration of renal graft function.

Acute Disease↗
PubMed1994

Cytomegalovirus reactivation and tumour necrosis factor.

Tumour necrosis factor-alpha (TNF) stimulates cytomegalovirus (CMV) activity in a transfected human monocytic cell line. We assessed whether this finding is relevant in vivo by evaluating the frequency of active CMV infection in patients with diseases that enhance plasma TNF. In septic disease, peripheral blood mononuclear cells of almost all patients studied were positive for CMV. Furthermore, CMV antigenaemia and enhanced plasma TNF occurred in many patients with liver cirrhosis, common variable immunodeficiency, and B-cell chronic lymphocytic leukaemia. Thus, TNF may have a central role in CMV reactivation.

Adolescent↗
PubMed1994

Binding of natural human IgM auto-antibodies to human tumor cell lines and stimulated normal T lymphocytes.

In a recent publication we described the binding of natural IgM antibodies derived from the human fetal B cell repertoire to the cell surface of some human tumor cells including colon carcinoma, small-cell lung cancer and B lymphoma lines [1]. Further analyses showed that a similar molecule was bound by the respective monoclonal human antibodies on the cell surface of polyclonally stimulated human CD3+ T cells, but is absent from unstimulated MNC. Both CD4+ and CD8+ stimulated cells were recognized. The molecule was found to be expressed together with lymphocyte activation markers (4F2, CD72, CD25). The membrane antigen expressed on both the activated T lymphocytes and tumor cells was characterized in a 2-D electrophoresis system: molecular weight 55-60 kDa, pI-approximately 6.0. Whereas the proliferation capacity of tumor cells was detected to be decreased significantly in the presence of the binding antibodies, no influence on [3H]thymidine uptake into stimulated T cells was found, suggesting different functional consequences of binding the respective antigen on malignant and normal cells. An interesting finding is the enhanced expression of major histocompatibility complex class I molecules on tumor cells incubated with human natural antibodies.

Antigens, Surface↗
PubMed1994

Precursor frequencies for DNA-specific B lymphocytes in patients with systemic lupus erythematosus (SLE).

Precursor frequencies for anti-DNA-secreting B cells were estimated in six healthy donors and 18 SLE patients with active and inactive disease. Precursors for IgG anti-dsDNA-secreting B cells were exclusively detected in SLE patients (73% of active patients and one inactive patient, 0.01-0.99% of IgG-producing B cells). These frequencies were in the same order of magnitude as frequencies of precursors for IgG anti-tetanus toxoid, which were detectable in three healthy volunteers after booster vaccination (0.07-0.8% of IgG-producing B cells), but not before (< 0.01%). Precursors for IgG anti-ss-DNA secreting B cells were observed in 33% of healthy donors and in 78% of SLE patients (0.01-0.32% of IgG-producing B cells). Only patient-derived IgG anti-DNA clones cross-reacted with (33%) or were monoreactive to dsDNA (12%). Precursors for IgM anti-DNA-secreting B cells were observed in healthy donors and SLE patients in comparable frequencies and with similar reactivities with ssDNA and dsDNA. Segregation analyses and sorting experiments showed that > 94% of clones secreting IgG anti-DNA were derived from in vivo sIgG+ B cells. sIgM+ B cells were induced to switch in vitro; however, only twice were cultures containing IgM and IgG anti-DNA antibodies observed under clonal conditions. In conclusion, our results indicate that precursor B cells for IgG anti-dsDNA in SLE patients are similarly selected and expanded as are precursor B cells specific for foreign antigens such as tetanus toxoid.

Adult↗
PubMed1994

Discordant expression of LFA-1, VLA-4alpha, VLA-beta 1, CD45RO and CD28 on T-cell subsets: evidence for multiple subsets of 'memory' T cells.

Several adhesion molecules and CD45RO have been reported to be upregulated on the cell surface of 'memory' T cells. Using triple-color flow cytometry, we compared the levels of typical 'memory' cell markers on peripheral blood T-cell subpopulations in a number of kidney transplant recipients, patients with systemic lupus erythematosus, newborn infants and healthy donors. CD45RO, VLA-beta 1 (CD29), VLA-5 alpha (CD49e), LFA-1 (CD11a/18), and CD2 were found to be closely coregulated on CD4+ T cells, while regulation of VLA-2 alpha (Cd49b), VLA-4 alpha (CD49d) and CD44 was quite discordant. In CD8+ T cells, by contrast, multiple subsets of 'memory'-type cells were distinguished. Unlike TCR alpha/beta T cells, which expressed either high or low levels of LFA-1, TCR gamma/delta cells all expressed high levels of LFA-1 (CD11a/CD18). Examination of T cells from kidney graft fine-needle aspiration biopsies during rejection revealed intragraft accumulation of 'memory'-type T cells expressing high levels of CD2 and LFA-1 (CD11a/CD18). Regarding peripheral blood T-cell subsets, differences between patients and healthy controls were only of a quantitative nature.

Adult↗