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Biomedical subjects

G Monneret

Publications and source records attributed to G Monneret.

At least 19 recordsLinked to original sources
PubMed2003

Marked improvement of the basophil activation test by detecting CD203c instead of CD63.

BACKGROUND: The flow cytometric basophil activation test by detection of CD63 expression has been developed as an alternative method for in vitro diagnosis of IgE-mediated reactions to various allergens. Despite promising initial studies, the test remains disappointing in terms of sensitivity. CD203c has recently been demonstrated as a specific activation marker of basophils that is rapidly up-regulated after allergen challenge in sensitized patients. OBJECTIVE: The goal of the present study was to compare basophil activation tests by using either CD203c or CD63 in the diagnosis of immediate-type allergy to latex. METHODS: Twenty-seven patients (health care workers of our institution) who developed clinical features evocative of allergy after contact with latex were included and classified into two groups. Group 1 (n = 16) comprised true allergic patients who presented with typical signs of immediate allergic reaction associated with a positive skin test (prick test). Group 2 (n = 11) consisted of patients whose clinical history was not typical and had negative skin test. Twelve healthy subjects were also studied as controls. We compared the sensitivity of two triple-staining flow cytometric protocols measuring basophil activation after latex stimulation: CD45-IgE-CD63 and CD45-IgE-CD203c. RESULTS: The CD203c protocol showed a higher sensitivity than the CD63 protocol (75% vs. 50%). In comparison, latex-specific IgE sensitivity was found to be 69%. Furthermore, the magnitude of the basophil response was significantly higher with CD203c in comparison with CD63. Specificity was 100% for both protocols. CONCLUSION: Due to superior gating of basophils and a higher range of activation in response to allergen, the basophil activation test is markedly improved by use of CD203c instead of CD63.

Adult↗
PubMed2001

Prostaglandin D2 is a potent chemoattractant for human eosinophils that acts via a novel DP receptor.

Prostaglandin D2 (PGD2) is released following exposure of asthmatics to allergen and acts via the adenylyl cyclase-coupled receptor for PGD2 (DP receptor). In this study, it is reported that human eosinophils possess this receptor, which would be expected to inhibit their activation. In contrast, it was found that prostaglandin D2 is a potent stimulator of eosinophil chemotaxis, actin polymerization, CD11b expression, and L-selectin shedding. These responses are specific for eosinophils, as neutrophils display little or no response to prostaglandin D2. They were not due to interaction with receptors for other prostanoids, as prostaglandins E2 and F(2alpha), U46619 (a thromboxane A2 analogue), and carbaprostacyclin (a prostacyclin analogue) displayed little or no activity. Furthermore, they were not shared by the selective DP receptor agonist BW245C and were not prevented by the selective DP receptor antagonist BWA868C, indicating that they were not mediated by DP receptors. In contrast, the prostaglandin D2 metabolite 13,14-dihydro-15-oxoprostaglandin D2 induced eosinophil activation but did not stimulate DP receptor-mediated adenosine 3',5'-cyclic monophosphate (cAMP) formation. These results indicate that in addition to the classic inhibitory DP1 receptor, eosinophils possess a second, novel DP2 receptor that is associated with PGD2-induced cell activation. These 2 receptors appear to interact to regulate eosinophil responses to PGD2, as blockade of DP1 receptor-mediated cAMP production by BWA868C resulted in enhanced DP2 receptor-mediated stimulation of CD11b expression. The balance between DP1 and DP2 receptors could determine the degree to which prostaglandin D2 can activate eosinophils and may play a role in eosinophil recruitment in asthma.

Actins↗
PubMed2001

Human gammadelta T cells express a higher TCR/CD3 complex density than alphabeta T cells.

The aim of our study was to compare CD3 expression on gammadelta T cells and alphabeta T cells in human patients. The antigen density of TCR and CD3 on both subsets was assessed by a quantitative method in eight patients. In parallel, we developed and validated a reliable direct tricolor staining protocol that we tested on samples from hospitalized and healthy individuals (n = 60). Our results demonstrate that human gammadelta T cells constitutively express approximately twofold more of the TCR/CD3 complex than alphabeta T cells. We suggest that this enhanced expression of the TCR/CD3 complex could contribute to the higher reactivity of gammadelta T cells compared to alphabeta T cells. These clinical laboratory results confirm the fundamental data described elsewhere. gammadelta T cells deserve further clinical investigations to understand their precise role in human immunity.

Adult↗
PubMed2001

Procalcitonin as an acute phase marker.

Procalcitonin is a 14-kDa protein encoded by the Calc-1 gene along with calcitonin and katacalcin. The function and regulation of this protein are quite different from those of the other gene products. Blood concentrations of procalcitonin are increased in systemic inflammation, especially when this is caused by bacterial infection. Studies of its behaviour in patients with bacterial sepsis have led to the proposal that it may be a useful marker of systemic bacterial infection, with greater specificity and sensitivity than acute phase proteins such as C-reactive protein.

Acute-Phase Reaction↗
PubMed2000

Procalcitonin and calcitonin gene-related peptide decrease LPS-induced tnf production by human circulating blood cells.

The pathogenesis of septic shock is mainly due to unregulated tumour necrosis factor-alpha (TNF-alpha) production. Procalcitonin (PCT) and calcitonin gene-related peptide (CGRP) are alternative transcription products of the calcitonin gene. Since high PCT levels have been described in human sepsis, and since CGRP inhibits TNF synthesis in rats, we examined the role of these peptides in the regulation of the inflammatory response during septic shock. LPS-induced TNF production was assessed using a human whole blood model. In this model, PCT (10(-7) M) and CGRP (10(-6) M) significantly inhibit TNF production by 27 and 24 % respectively. The effect of CGRP was reversed by CGRP 8-37 (10 microM), an antagonist of CGRP receptor. No effect on interleukin (IL)-1, IL-6 and IL-8 was found. This is the first description of an anti-inflammatory role for PCT and CGRP in humans.

Animals↗
PubMed2000

Factors that predict chemotherapy-induced myelosuppression in lymphoma patients: role of the tumor necrosis factor ligand-receptor system.

PURPOSE: To analyze factors that predict the occurrence of chemotherapy-induced myelosuppression and, in particular, the role of the tumor necrosis factor (TNF) ligand-receptor system in lymphoma patients at the beginning of their treatment. PATIENTS AND METHODS: We investigated the predictive factors for myelosuppression after the first course of chemotherapy in a cohort of 101 consecutive, previously untreated lymphoma patients receiving regimens that include doxorubicin and cyclophosphamide. Plasma samples were tested at baseline by enzyme-linked immunosorbent assay for TNF and its soluble receptors. Univariate and multivariate analyses were performed with a forward regression procedure that included all of the parameters that were found to be significant in the univariate analysis. The dose of chemotherapy and the prophylactic treatment with granulocyte colony-stimulating factor were deliberately included in this model. RESULTS: Sixty-seven patients experienced World Health Organization (WHO) grade 4 neutropenia, and 37 patients experienced febrile neutropenia, which was responsible for WHO grade 2 through 4 infections in 23 patients. In multiparametric regression analysis, the occurrence of grade 4 neutropenia was associated with high doses of cyclophosphamide (odds ratio ¿OR, 19.8; P =.008) and high levels of soluble p75-R-TNF (OR, 8.52; P =.001). The duration of grade 4 neutropenia for more than 5 days was associated with the lack of hematopoietic growth factor administration (OR, 6.76; P =.004) and high levels of soluble p75-R-TNF (OR, 5.84; P =.0023). The occurrence of febrile neutropenia was associated with high doses of cyclophosphamide (OR, 4.7; P =.007), altered performance status (OR, 18.8; P <.0001) and high levels of soluble p75-R-TNF (OR, 3.49; P =.029). CONCLUSION: This study indicates that in addition to the dose of chemotherapy and the administration of hematopoietic growth factors, poor performance status and high p75-R-TNF levels can predict the occurrence of chemotherapy-induced myelosuppression in lymphoma patients. This model may help in selecting patients for prophylactic growth factor administration.

Adult↗
PubMed2000

The clinical usefulness of the measurement of cytokines.

The utilization of accurate and sensitive methods for the measurement of cytokines in body fluids is prerequisite for the proper use of these mediators in clinical practice. Many factors contribute to the complexity of cytokine quantitation. Bioassays historically preceded immunoassays, which are now very popular, but there is a need for standardization. Nevertheless, due to the local effects of cytokines, the study of their blood levels is of limited value for an understanding of the pathophysiology of these mediators. This explains the development of alternative approaches to assess the ability of cells to produce cytokines. These include the Enzyme-Linked Immuno Spot Assay (ELISPOT), the measurement of cell-associated cytokines by flow cytometry, and the study of cytokine secretion by isolated peripheral blood mononuclear cells or by whole blood test. All these techniques, associated with a local detection of cytokines by immunohistochemistry or in situ hybridization and reverse transcriptase polymerase chain reaction, appear to be complementary tools for a better understanding of the biology of cytokines. Selected examples of possible clinical applications related to infectious diseases, cancer, autoimmune diseases, allergy, transplantation and preclinical evaluation of drugs and biotechnology products are given.

Body Fluids↗
PubMed1999

Multicenter evaluation study on a new HEp2 ANA screening enzyme immune assay.

The COBAS Core HEp2 ANA enzyme immune assay (EIA) was evaluated in a precision and a clinical sample study in comparison to indirect immunofluorescence assay (IFA) on HEp2-cells. In the precision study the COBAS Core EIA yielded intraassay coefficient variations (CVs) mostly below 9%, and interassay CVs between 4.7% and 10.4%. When comparing the COBAS Core EIA to IFA, the results corresponded well in healthy subjects, systemic lupus erythematosus, mixed connective tissue disease and rheumatoid arthritis. In the case of Sjögren's syndrome and scleroderma patients the COBAS Core EIA yielded a lower rate of positive results compared to IFA. This discrepancy may be explained by the lack of detection of autoantibodies to nuclear antigens that can be identified only by IFA due to their compartmentalization and higher localized antigen density in HEp2 cells. The discrepancies in the group of dermato/polymyositis patients are due to the fact that the EIA contains mainly nuclear antigens and was able to detect only antibodies against the cytoplasmic Jo1 antigen that was added to the HEp2 nuclear extract. Routine sera were also evaluated; good agreement was found in sera from patients attending tertiary reference centres for autoimmune diseases but a higher number of discrepancies was reported in sera from unselected populations.

Adult↗
PubMed1999

Detection of allergen-induced basophil activation by expression of CD63 antigen using a tricolour flow cytometric method.

In the field of allergy diagnosis, most in vitro functional tests are focused on basophils. Nevertheless, the very small number of circulating basophils limits these experiments and their clinical benefit remains controversial. As flow cytometry is a valuable tool for identifying cell populations, even at low concentrations, we developed a tricolour flow cytometric method for the study of allergen-induced basophil activation. Identification of cells was based both on CD45 expression and on the presence of IgE on the cell surface, since basophils express high-affinity receptors for IgE (Fc epsilon RI). Cell activation upon allergen challenge was assessed by the expression of CD63 antigen on the plasma membrane. Basophil isolation and activation (with the chemotactic peptide formyl-methionyl-leucyl-phenylalanine) were validated in 32 non-allergic patients. In 12 allergic patients, basophil stimulation by a relevant allergen was in most cases positive (10/12). Furthermore a concentration-dependent hook effect was observed. Of the allergic and non-allergic patients, none showed non-specific activation with an irrelevant allergen (specificity 100%). Overall, our preliminary results, even in a small population, suggest that this is a reliable and valuable method for the diagnosis of allergies complementing specific allergen IgE and skin test results. Obviously, additional clinical studies are needed to validate these first results.

Adolescent↗
PubMed1999

Renal effects of cP450 arachidonate metabolites in the Lyon hypertensive rat.

This study is aimed at evaluating the influence of the cytochrome P450 arachidonate metabolites on the renal alterations exhibited by the Lyon hypertensive (LH) rat. To that purpose, kidneys were isolated from LH rats and their normotensive (LN) controls and single-pass perfused at different pressure levels before (control conditions) and after cytochrome P450 inhibition by 7-ethoxyresorufin (7-ER, 1 microM). In control conditions, LH kidneys differed from LN ones by an increased preglomerular resistance and a blunted pressure natriuresis. 7-ER, which did not affect the function of LN kidneys, decreased the vascular resistance of LH kidneys, increased their glomerular filtration rate but had no effect on their pressure natriuresis. These results indicate that the renal cytochrome P450 arachidonate metabolism differs between LN and LH rats and is presumably involved in the functional alterations exhibited by LH kidneys.

Animals↗
PubMed1999

[Biological diagnosis of immediate drug allergy. Comparative study of histamine liberation tests and CD63 expression by flow cytometry (preliminary results)].

The diagnosis of drug allergy is mainly based upon a detailed clinical history, positive skin tests (ST) and detection of specific IgE. In case of discrepant results, in vitro investigations to identify the responsible drug are needed. The histamine release test (HR) is usually performed. Nevertheless, its clinical benefit remains controversial. Flow cytometric methods (FCM) for the study of allergen induced basophil activation have been recently described. We assessed their usefulness in the diagnosis of drug allergy in comparison to HR results. Eighteen patients were included and 24 drugs (mainly antibiotics and muscle relaxant drugs) were tested. On the basis of clinical signs, 15 patients were classified as allergic (18 drugs). Sensitivity of biological investigations were found as follows: 71% (ST), 71% (FCM) and 24% (HR). This suggests performing FCM rather than HR. In addition, HR is more costly in terms of both reagents and laboratory technician time. Thus, CD63 detection by FCM seems to be a more reliable method in the clinical immunology laboratory. Additional data are needed to validate these preliminary results (sensitivity and specificity, especially in atopic patients) and to assess the interest of the method to investigate drug allergy due to other types of molecules.

Antigens, CD↗
PubMed1998

Cytokine assays in human sera and tissues.

The use of accurate and sensitive methods for the measurement of cytokines in body fluids is an absolute prerequisite for the proper use of these mediators in clinical practice. Many factors contribute to the complexity of cytokines quantitation: these molecules circulate at very low levels (e.g. pg/ml) under various molecular forms, the existence of circadian rhythms has been described, and the presence of inhibitors (binding proteins, soluble receptors, autoantibodies) can potentially interfere in the assays. Blood collection for cytokines needs particular attention to prevent possible contamination by endotoxins, which can trigger cytokines cellular production after sampling. Bioassays historically preceded immunoassays; the latter techniques are now very popular, but there is an urgent need for standardisation between the different kits commercially available. Nevertheless, due to the essentially local effects of cytokines, the study of their circulating levels only represents the 'tip of the iceberg' and is of limited value for a global understanding of the pathophysiology of these mediators. This explains the development of other approaches to assess the ability of cells to produce cytokines. These include the ELISPOT assay, the measurement of cell-associated cytokines by flow cytometry, and the study of cytokine secretion by isolated peripheral blood mononuclear cells or by whole blood test. All these techniques, associated with a local detection of cytokines by immunohistochemistry or in situ hybridization and reverse transcriptase polymerase chain reaction (RT-PCR), appear to be complementary tools for a better understanding of the multiple aspects of the biology of cytokines.

Biological Assay↗
PubMed1997

Procalcitonin and C-reactive protein levels in neonatal infections.

In order to assess the potential fo procalcitonin measurement in the management of neonatal sepsis, daily variations in serum procalcitonin (measured by an immunoluminometric assay) were evaluated in 94 control and infected newborn infants in comparison to C-reactive protein (measured by an immunonephelometric method). High levels of procalcitonin correlated with bacterial invasion and showed no discrepancies with C-reactive protein. procalcitonin increased (up to 400 micrograms l-1 and returned to the normal range (< 0.1 microgram l-1) more quickly than C-reactive protein, suggesting that procalcitonin may be an early marker of favourable outcome. Another finding is a significant procalcitonin peak on the first day of life in the control group, independent of any infectious stimulus. In conclusion, procalcitonin seems to be an interesting marker of neonatal sepsis but additional investigations are needed to understand better its mechanism of synthesis in order to determine its clinical usefulness.

Bacterial Infections↗