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Biomedical subjects

B Vray

Publications and source records attributed to B Vray.

At least 37 records · Page 2Linked to original sources
PubMed1996

Nitric oxide production is increased in patients after burn injury.

OBJECTIVE: Human burn injury is associated with an inflammatory response and related hyperdynamic cardiovascular profile. Increased production of nitric oxide (NO), a potent endogenous vasodilator, has been reported in patients with inflammatory states, including sepsis, but not after trauma other than burns. We studied whether plasma levels of the stable byproducts of NO, nitrite (NO2-) and nitrate (NO3-), are increased in burn patients. DESIGN: Prospective controlled study. PATIENTS AND METHODS: In consecutive patients admitted to the intensive care unit of the burn center at the Queen Astrid Military Hospital in Brussels, plasma was drawn daily from day 1 to day 5 postadmission for determination of NO2-/NO3- levels (Griess' reaction). In a control group of nonseptic inpatients from the department of neurology in Erasme University Hospital who were matched for nutrition (30 to 40 kcal/kg/day of a standard enteral solution), plasma was drawn once for NO2-/NO3- determination. MEASUREMENTS AND MAIN RESULTS: The burn group included 16 patients (age 35 +/- 18 years, total burn surface area (TBSA) 37 +/- 19%) and the control group included six patients (age 64 +/- 18 years). For each comparison between the groups, NO2-/NO3- plasma levels were higher in those patients with burns than in the control group. In the burn group, there was no correlation between NO2-/NO3- plasma levels and TBSA, age, TBSA x age, blood pressure or time. However, in a subgroup of five burned patients who became septic during the study period, NO2-/NO3- plasma levels were slightly higher than in the non-infected patients (177 +/- 131 vs. 83 +/- 48 micromoles/L, NS). CONCLUSION: Human burn injury is associated with an increase in NO production. In this small-size study, NO production was not proportional to burn area, and seemed to be further enhanced in septic patients.

Adolescent↗
PubMed1996

Granulocyte-macrophage colony-stimulating factor: involvement in control of Trypanosoma cruzi infection in mice.

Several cytokines play crucial roles in Trypanosoma cruzi infection in mice, but the involvement of endogenous granulocyte-macrophage colony-stimulating factor (GM-CSF) is poorly documented. This report shows that T. cruzi infection of mice triggered an early and sharp increase in plasma GM-CSF during the ascending phase of parasitemia. The plasma GM-CSF concentration remained stable at the peak of parasitemia and subsequently increased in those mice that survived to the acute phase. GM-CSF level increased again sharply, while parasitemia was rapidly decreasing. Finally, GM-CSF was undetectable, soon after the disappearance of circulating parasites. Injection of T. cruzi-infected mice with neutralizing anti-GM-CSF monoclonal antibodies induced the early appearance of parasitemia and aggravated cumulative mortality. In contrast, recombinant mouse GM-CSF (rmGM-CSF) caused sharp decreases in both parasitemia and cumulative mortality in T. cruzi-infected mice. Peritoneal macrophages from rmGM-CSF-treated and infected or uninfected mice were less infected ex vivo than those from control mice. Taken together these data demonstrate the protective action of endogenous GM-CSF in T. cruzi infection. Neutralization of endogenous GM-CSF aggravates infection, while exogenous rmGM-CSF decreases both parasitemia and host mortality.

Animals↗
PubMed1995

IFN-gamma receptor-deficient mice are hypersensitive to the anti-CD3-induced cytokine release syndrome and thymocyte apoptosis. Protective role of endogenous nitric oxide.

Mice with a disruption of the IFN-gamma receptor alpha-chain gene (IFN-gamma R alpha o/o mice) were found to be significantly more sensitive than their wild-type counterparts to induction of the anti-CD3-induced disease syndrome. Specifically, when given a selected dose of anti-CD3 Ab, IFN-gamma R alpha o/o mice developed severe hypothermia and hypoglycemia, leading to 100% mortality within 72 h. In contrast, wild-type mice failed to develop overt pathologic manifestations and survived. Histologic examination revealed apoptosis in thymuses and spleens, which were significantly more pronounced in the mutant than in the wild-type mice, as confirmed by flow cytometric and DNA electrophoretic analysis. Apoptosis affected mainly CD4+CD8+ and CD4+CD8- thymocytes. Other histologic alterations were steatosis in livers, and erythrocyte extravasation and infiltration of apoptotic cells in lungs, all of which were exclusively observed in IFN-gamma R alpha o/o mice. Blood levels of TNF, IL-2, IL-6, and IL-10 were slightly more elevated in IFN-gamma R alpha o/o mice, but insufficiently so to explain increased disease severity. Thus, even more elevated cytokine levels in wild-type mice receiving high doses of anti-CD3 Ab were not associated with morbidity or apoptosis. Blood levels of IFN-gamma were barely detectable in anti-CD3-challenged wild-type mice, but were relatively high in the mutant mice. Increased susceptibility of IFN-gamma R alpha o/o mice was associated with impaired nitric oxide (NO) production, as indicated by significantly lower plasma nitrite levels and by more transient expression of spleen inducible NO synthase mRNA. Moreover, treatment of wild-type mice with the NO synthase inhibitor N-nitro-L-arginine methylester resulted in increased anti-CD3-induced morbidity and mortality. The data indicate that IFN-gamma R alpha o/o mice produce less NO and are therefore more sensitive than wild-type mice to the deleterious effect of anti-CD3 Ab.

Animals↗
PubMed1995

Relationship between granulocyte macrophage-colony stimulating factor, tumour necrosis factor-alpha and Trypanosoma cruzi infection of murine macrophages.

Gamma interferon (IFN-gamma)-activated macrophages control Trypanosoma cruzi infection via nitric oxide (NO), recently recognized as a major effector molecule. Granulocyte macrophage-colony stimulating factor (GM-CSF) is a multipotent cytokine secreted by macrophages and many other cells. It induces the production of tumour necrosis factor alpha (TNF-alpha), another cytokine also secreted by macrophages and involved in the control of T. cruzi infection. However, no data are available on the relationship between GM-CSF, TNF-alpha and NO produced by macrophages activated by IFN-gamma and infected with T. cruzi. To highlight this relationship, mouse peritoneal macrophages (MPM) and two c-myc retrovirus-induced macrophage cell lines (9.1.1 and BMM8), respectively characterized by a constitutive and an inducible production of GM-CSF, were activated with IFN-gamma and/or GM-CSF and infected with T. cruzi. Our results indicate that T. cruzi upregulates GM-CSF release from MPM and from the two macrophage cell lines, activated (or not) by IFN-gamma. A high autocrine production of GM-CSF or an exogenous supply of GM-CSF is correlated with an enhanced release of TNF-alpha and NO, inducing an improved control of T. cruzi infection by IFN-gamma-activated MPM.

Animals↗
PubMed1995

Impaired protein catabolism in Trypanosoma cruzi-infected macrophages: possible involvement in antigen presentation.

The effect of Trypanosoma cruzi infection on the ability of mature and immature murine peritoneal macrophage (MPM) subpopulations to catabolize the bacteriophage lambda repressor cI protein (cI) has been investigated. The capacity of infected MPM to present the cI and to stimulate various CD4+, I-Ad- or I-Ed-restricted T-cell hybridomas specific for cI was also assessed. Our results show that the radioiodinated cI uptake and catabolism decreased sharply after infection of MPM with T. cruzi. A cI presentation deficiency appeared in mature and immature MPM infected with T. cruzi trypomastigotes. The ability of infected MPM to bind immunogenic cI (12-26) peptides to the plasma membrane Ia molecules was also altered, especially in immature MPM, as shown with paraformaldehyde prefixed MPM, suggesting that these MPM only have a few functional Ia molecules on their membrane. The reduced capacity of cI presentation to the I-Ed-restricted B26.1 hybridomas by infected MPM subpopulations was comparable to that of the I-Ad-restricted B24.4 and B26.2 T cells. The percentage of major histocompatibility complex (MHC) class II-positive MPM was also reduced after T. cruzi infection. The percentage of positive interleukin-2 receptor (IL-2R) MPM was sharply lowered in infected cells, even with a pre- or a post-interferon-gamma (IFN-gamma) activation. Finally, inhibition of prostaglandin with indomethacin, or of nitric oxide with N-monomethyl-L-arginine, or of tumour necrosis factor-alpha (TNF-alpha) with specific monoclonal antibodies did not restore the cI presentation capacities of the MPM subpopulations. Taken together, these results suggest that T. cruzi infection induces a reduced capacity for macrophages to take up and catabolize antigen, resulting in a deficient antigen processing and presentation of the derived immunogenic peptides to specific CD4+ T-helper type-1 cell hybridomas. The decreased cI presenting capacity was a function of the cell's burden and maturity.

Animals↗
PubMed1994

Separation of murine peritoneal macrophages using Percoll density gradients.

Macrophages harvested from the murine peritoneal cavity are functionally and morphologically heterogeneous. Here, we describe a procedure which permits the determination of specific cell densities using a continuous density gradient of Percoll (analytical step). Subsequently, discontinuous density gradients are used in routine (preparative step) to isolate all the cell subpopulations according to their actual specific density. This procedure has been successfully used for both mouse and rat peritoneal macrophages.

Animals↗
PubMed1994

Immunophenotyping of murine peritoneal macrophages and lymphocytes by flow cytometry.

Peritoneal cells include mainly macrophages and both T and B lymphocytes. We describe a simple procedure to analyze by flow cytometry the antigens expressed on macrophage and/or lymphocyte membranes. F4/80 and CR3 macrophage antigens were detected with anti-F4/80 and anti-Mac-1 monoclonal antibodies (mAb) respectively, CD4 and THY1.2 T lymphocyte antigens with GK1.5 and J1j mAbs respectively, B CD5 lymphocytes were identified with LY1.2 mAb and Fc gamma RII/Fc gamma RIII were detected with 2.4G2 mAb.

Animals↗
PubMed1994

Quantification of bacterial phagocytosis by flow cytometry and spectrofluorimetry.

Bacterial phagocytosis is a cardinal function of phagocytes. We describe a simple procedure to easily quantify this function using fluoresceinated bacteria. Non-ingested bacteria and those adsorbed to the cell membrane are eliminated by an enzymatic procedure. Only macrophages with ingested fluorescent bacteria are detected, thereby permitting an accurate quantification of the phagocytic process by both spectrofluorimetric measurement and flow cytometric analysis.

Animals↗
PubMed1994

Interferon-gamma-activated immature macrophages exhibit a high Trypanosoma cruzi infection rate associated with a low production of both nitric oxide and tumor necrosis factor-alpha.

Murine peritoneal macrophages (MPM) can be subdivided into two subpopulations of mature and immature macrophages. In contrast to mature macrophages, immature ones were highly susceptible to Trypanosoma cruzi infection. This highly susceptibility was associated with a low production of alpha 2-macroglobulin. Interferon-gamma (IFN-gamma)-activated immature macrophages also exhibited a higher infection rate than did IFN-gamma-activated mature ones. This higher rate of infection was associated with a low production of both nitric oxide (N = O) and tumor necrosis factor-alpha (TNF-alpha). In contrast, mature MPM showed a lower rate of infection and produced higher levels of N = O and TFN-alpha. Taken together, these results show a clear-cut difference in the course of T. cruzi infection in relation to the macrophage maturation state.

Animals↗
PubMed1994

Modulation of T-cell responsiveness during Trypanosoma cruzi infection: analysis in different lymphoid compartments.

Spleen and lymph node cells of Trypanosoma cruzi-infected mice were studied for mitogen-induced responsiveness in terms of proliferation and lymphokine production (IL-2, IFN-gamma). Splenocyte (SP) as well as lymph node cell (LN) proliferation and IL-2 production were depressed during the acute phase of the infection. Proliferative capacity of LN cells recovered completely and that of SP partially during the chronic phase. In contrast to these suppressive effects, the mitogen-induced IFN-gamma response was enhanced. In vitro co-incubation of normal SP or LN cells with trypomastigotes resulted in a reduced mitogen-induced cell proliferation and IL-2 secretion, similar to those seen with cells taken from infected mice. In contrast, trypomastigotes exerted a stimulatory activity on the mitogen-induced IFN-gamma response of both SP and LN cells. Addition of lymph node cells from T. cruzi-infected mice (LN-I) to lymph node cells of control mice (LN-C) suppressed strongly the mitogen-induced responsiveness of such cocultures. A marginal level of suppression was recorded in cocultures of spleen cells from infected mice (SP-I) and control spleen cells (SP-C). The potent suppressive cells within LN-I populations were identified as macrophage-like and such cells were absent in SP-C and peritoneal exudate cells from T. cruzi infected animals.

Acute Disease↗
PubMed1993

Mouse peritoneal macrophages: characterization of functional subsets following Percoll density gradients.

Mouse resident peritoneal cells were separated into twelve fractions on Percoll gradients according to their specific density and were thoroughly characterized by Giemsa staining, some biochemical assays, immunophenotyping and phagocytic tests. Among these fractions, the macrophages were mainly represented in 7 subsets of 1.073 to 1.104 g/ml densities. The results of this study emphasize that resident peritoneal macrophages of primo-explantation can be divided into two distinct subpopulations with separate functions, related to the stage of cell maturity. In fact, our results show that one macrophage subpopulation is rich in immature cells, characterized by their peroxidative activity, the expression of F4/80 antigen, Mac-1 and Fc receptors, in correlation with their high specific density; the second subpopulation contains mature macrophages (lower percentage of peroxidase-positive cells) with lower densities and a lower level of expression of the above-mentioned molecules. Antibody-dependent and antibody-independent bacterial phagocytosis, the phagocytic index and Fc gamma RII rosetting increased together with the cell density, and were elevated in the immature cell subpopulation. T and B lymphocytes were also identified in all the macrophage subsets, but in a low proportion.

Animals↗
PubMed1993

Trypanosoma cruzi upregulates nitric oxide release by IFN-gamma-preactivated macrophages, limiting cell infection independently of the respiratory burst.

The relationship between nitric oxide (N = O) produced by mouse peritoneal macrophages (MPM) and Trypanosoma cruzi infection is still poorly understood. The conditions of MPM activation by gamma-interferon (IFN-gamma) to trigger a N = O-dependent trypanocidal activity, as well as the effect of parasite infection or of reactive oxygen species (ROS) inhibitors on the N = O release were studied. T. cruzi infection occurring after a previous 24 h MPM activation induced an enhancement of nitrite levels (the stable degradation product of N = O) in cell supernatants; both the percentage of infected MPM and the number of amastigotes per infected cell were decreased in comparison to infected but non-activated MPM. Addition of superoxide dismutase or catalase to non-infected but activated MPM increased the nitrite levels; these were not detectable when L-arginine inhibitors were added together with ROS inhibitors. The latter had no effect on infection nor on nitrite levels when infection occurred after pre-activation, and induced only a weak nitrite release when infection took place before MPM activation. Altogether, these results support the involvement of N = O in the inhibition of T. cruzi infection by IFN-gamma-preactivated macrophages, together with the upregulation of N = O release by T. cruzi infection independently of the respiratory burst.

Animals↗
PubMed1992

Eicosanoids modulate CR1- and Fc-dependent bacterial phagocytosis.

It is known that macrophages produce large amounts of eicosanoids during phagocytosis and that pharmacological concentrations of prostaglandin E2 (PGE2) inhibit phagocytosis in several models. However, the physiological effect on phagocytosis of endogenous prostaglandins, produced during CR1- or FcR-mediated bacterial phagocytosis, remains unclear. In this study, we show that indomethacin inhibits the CR1- but not the FcR-dependent phagocytosis of bacteria by rat peritoneal cells in the same range of concentrations that inhibit the synthesis of PGE2, PGI2 and thromboxane A2. An exogenous supply of PGE2 and PGE1 (10(-10) to 10(-8) M) restored the CR1-mediated phagocytosis; higher concentrations were inhibitory. Our data indicate that PGE2 and/or PGI2, produced by rat peritoneal cells, are involved in CR1-dependent bacterial phagocytosis.

Alprostadil↗
PubMed1991

Trypanosoma cruzi but not Trypanosoma brucei fails to induce a chemiluminescent signal in a macrophage hybridoma cell line.

Macrophage-Trypanosoma cruzi interactions were studied by using a newly generated macrophage hybridoma cell line (2C11-12) that was selected for its capacity to produce high levels of reactive oxygen intermediates. This cell line was found to be a suitable host cell for T. cruzi, and intracellular parasitic development could be inhibited by activation with gamma interferon. When exposed to opsonized Trypanosoma brucei, Micrococcus lysodeikticus, or Legionella pneumophila, the activated macrophage cell line produces a high chemiluminescent signal, indicating the release of reactive oxygen intermediates. Alternatively, when opsonized T. cruzi was added to these activated macrophages, this parasite failed to stimulate a chemiluminescent response, suggesting an impairment in the triggering of the respiratory burst.

Animals↗
PubMed1988

Macrophage heterogeneity in prostaglandins and thromboxane synthesis: differential activation by Fc- and C3b-dependent bacterial phagocytosis.

Resident peritoneal macrophages, obtained from rats, were separated into subpopulations by centrifugation on a Percoll discontinuous density gradient. Nine fractions of pure macrophages were isolated. Each subpopulation was studied for Fc- and C3b-dependent bacterial phagocytosis and assayed for the related synthesis of PGE2, TxA2 and PGI2, measured by their stable metabolites TxB2 and 6-Keto-PGF1. The results show that with decreasing density, which corresponds to a greater maturity, the production of PGE2 increases and that of TxB2 and 6-Keto-PGF1 decreases. The cells of low density were mostly stimulated by IgG-opsonized bacteria, whereas those of high density responded preferentially to C3b- opsonized bacteria. This pattern is roughly similar to the one characterizing the phagocytosis via these two receptors although the correlation is not absolute. It can be concluded that enzymes involved in the metabolism of arachidonic acid, as well as receptors for C3b and IgG, are differentially expressed among resident macrophage subpopulations and thus during macrophage maturation.

Animals↗
PubMed1987

Partial characterization of a Legionella pneumophila serogroup 1 immunodominant antigenic determinant recognized by a monoclonal antibody. Legionella specific antigenic determinant.

A monoclonal antibody was used to characterize a serogroup 1 specific Legionella pneumophila Philadelphia strain 1 antigenic determinant. A quantitative fluorometric assay was developed to quantitate the antibody sites (2.7 +/- 0.4 X 10(5)) on Legionella bacteria and to determine the physico-chemical parameters of the antibody-antigen interaction (at 4 degrees C: delta G = -10.9 Kcal X mol-1, delta H = 1.7 Kcal X mol-1, delta S = 45 cal X K-1 X mol-1). The same method was used to study the modification or the removal of the antigen by chemical and enzymatic means (trypsin, papain, lysozyme, acetone, chloroform-methanol and Tris-EDTA); only Tris-EDTA extraction resulted in a significant decrease in antibody binding sites. Inhibition studies of the fluorescein-labelled antibody binding were performed with different sugars of which only L-fucosylamine was inhibitory, and with other monoclonal antibodies to Legionella pneumophila serogroup 1 in order to compare their fine specificity and affinity. The results indicate that the epitope recognized was an immunodominant carbohydrate including an aminodideoxyhexose and carried by the lipopolysaccharide.

Antibodies, Bacterial↗