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Biomedical subjects

Y Lebranchu

Publications and source records attributed to Y Lebranchu.

At least 73 records · Page 4Linked to original sources
PubMed1996

Docosahexaenoic and eicosapentaenoic acids inhibit human lymphoproliferative responses in vitro but not the expression of T cell surface activation markers.

The effects of polyunsaturated fatty acids (PUFAs: docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids) on induced lymphocyte proliferation and expression of CD25alpha chain of interleukin-2 receptor, CD71 and HLA-DR were investigated. PUFAs had no effect on phytohaemagglutinin (PHA)-induced lymphocyte agglutination, but they strongly inhibited the lymphoproliferative response to PHA. This inhibitory effect is PUFA dose-dependent and seems to be more potent with DHA than EPA, Pre-incubation experiments showed that lymphocytes cultured with PUFAs for 6 h then washed and exposed to PHA, still inhibited lymphocyte proliferation. The authors also showed that this inhibitory activity was time dependent but became nonsignificant when PUFAs were added after 48 h lymphocyte culture. The addition of excess exogenous human recombinant rIL-2 partly restored PHA-lymphocyte proliferation inhibited by EPA but not by DHA. On the other hand, the authors showed that PUFAS did not inhibit IL-2 stimulated lymphocyte proliferation. The addition of PUFAs to cell culture medium had no inhibitory action on the PHA-induced lymphocyte expression of CD25, CD71 and HLA-DR. Furthermore, this effect appeared independent of eicosanoid synthesis or peroxide formation. Indeed, the inclusion of aspirin and vitamin E in the culture medium did not prevent the inhibitory effects of PUFAs on lymphocyte proliferation. Regardless of the mechanism of action, the inhibitory effect of PUFAs on activated lymphocytes may explain why some clinical trials of fish oil supplemented diets containing high amounts of DHA and EPA have been successful in improving the health status of patients suffering from inflammatory and autoimmune disorders.

Adult↗
PubMed1995

A simplified and low-cost one-stage chromogenic assay for tissue factor dependent procoagulant activity of endothelial cells.

We developed a sensitive tissue factor (TF) chromogenic assay on a limited number of endothelial cells (EC), performed in microtiter plates, and which uses a normal pooled human plasma instead of purified concentrates as a source of coagulation factors. Primary cultures of human umbilical vein EC (HUVEC), both unstimulated and stimulated by lipopolysaccharide (LPS) were incubated with 50 microliters of of diluted normal human plasma (NHP) and 50 microliters of Factor Xa-specific chromogenic substrate (CBS 31-39, Stago, France). Hirudin was added at 4 U/ml to the plasma/CBS 31-39 mixture to inhibit thrombin generation. Optical densities were read at 405 nm and corresponding amounts of generated factor Xa were expressed in mU Xa/well using a standard curve established with purified human Factor Xa. The following parameters were then defined: the number of EC to plate (10(4) EC/well of a 96-well plate), the plasma-test dilution (1:20), the concentration of CBS 31-39 (0.50 mM) and the incubation time of reagents with EC (2 hours). The procoagulant activity (PCA) measured was only dependent on TF since it was no longer detectable either when FVII-deficient plasma was tested instead of normal human plasma or when PCA assays were performed in the presence of a blocking anti-human TF monoclonal antibody. This method allowed detection of a TF-dependent PCA on as few as 1000 EC per well. In addition, TF expression equal to 50% of maximal values was measured with LPS concentrations as low as 1 ng/ml, supporting the high sensitivity of the assay.

Blood Coagulation↗
PubMed1995

Evidence of noninvolvement of swine MHC class II in the in vitro proliferative response of human lymphocytes to porcine endothelial cells.

Successful pig-to-human xenotransplantation may expose swine endothelium to the human immune system. Since endothelial MHC class II expression is crucial in the genesis of an allogeneic lymphocyte response, the involvement of porcine MHC (SLA) class II molecules in the induction of human lymphocyte proliferation was studied. When cocultured with a confluent monolayer of irradiated porcine aortic endothelial cells (PAEC), human peripheral blood mononuclear cells (PBMC) incorporated tritiated thymidine. Monocyte depletion strongly reduced the magnitude of the lymphocyte proliferative response. Resting cultured PAEC were SLA class II-negative and an induction of these molecules during the xenogeneic mixed lymphocyte endothelial cell culture (XMLEC) was not observed. Moreover, the addition of an antibody directed against the SLA-DR molecule was without effect. Lymphocyte proliferation was also studied in response to SLA class II-positive stimulating cells--either human TNF-alpha-stimulated PAEC or porcine splenocytes. Induction of SLA class II molecules on PAEC had no effect on the human PBMC proliferative response. Moreover, human PBMC did not proliferate in response to porcine splenocytes. These results suggest (1) that SLA class II molecules are not involved in the induction of the human lymphocyte proliferative response and (2) that the endothelial nature of the stimulating cells plays a key role in this proliferation.

Animals↗
PubMed1995

Tissue factor activity of syncytiotrophoblast plasma membranes and tumoral trophoblast cells in culture.

During pregnancy, important modifications of hemostasis occur resulting in mothers in hypercoagulability and the role of placental cells such as trophoblast cells has been hypothesized. In this study, we first showed that syncytiotrophoblast plasma membranes, isolated from normal human placenta, expressed a strong tissue factor (TF) activity. We then studied TF activity of two continuous trophoblast cell lines (JEG-3 and BeWo) in comparison to human umbilical vein endothelial cells (HUVEC) and transformed human endothelial cells (ECV-304). TF assays were performed on intact detached confluent cells. Unstimulated JEG-3 and BeWo cells exhibited a very high TF activity which slightly increased after 2 to 4 h TNF-alpha stimulation. In contrast, HUVEC and ECV-304 had a lower basal TF activity which was mainly inducible by TNF-alpha, with a maximum effect after 4 to 6 h stimulation. For both cell types, TF activity was decreased to basal value after 16-hour TNF-alpha stimulation. These results support that trophoblast cells are able to express TF but the involvement of this property in the hemostatic physiological changes observed during pregnancy, remains to be demonstrated.

Cell Line, Transformed↗
PubMed1994

Adhesive properties of choriocarcinoma cells toward lymphocytes activated or not by interleukin-2.

Choriocarcinoma cells (CC) in vitro are resistant to NK lysis but sensitive to lysis by blood or decidual effectors activated by interleukin-2 (IL-2). Because lytic activity requires a step of adhesion, the adhesive properties of the choriocarcinoma cells BeWo, JEG-3, and JAR were examined functionally toward peripheral blood lymphocytes. The adhesion of lymphocytes to choriocarcinoma cells was very low and did not increase after stimulating lymphocytes with IL-2. As demonstrated by cytofluorimetry analysis, choriocarcinoma cells and cytotrophoblast cells prepared from term placenta expressed intercellular adhesion molecule-1 (ICAM-1), whereas only CC expressed CD56. Tumor necrosis factor-alpha or interferon-gamma increased the expression of ICAM-1 on choriocarcinoma cells without modifying the adhesion of lymphocytes to choriocarcinoma cells. These results suggest that resistance of choriocarcinoma cells to lysis by cytotoxic effectors could partially be attributed to the low level of lymphocyte adhesion to these cells.

Cell Adhesion↗