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Biomedical subjects

G Vezon

Publications and source records attributed to G Vezon.

At least 37 records · Page 2Linked to original sources
PubMed1993

Measurement of residual leukocytes in platelet concentrate units.

Leukocyte contamination of various blood products is implicated in febrile transfusion reactions, in alloimmunization phenomena and immunosuppression, and in the transmission of viral infections. The biggest difficulty in interpreting published reports lies in the methods used to quantify residual leukocytes. As automated cell counters are not precise and sensitive enough to detect low cell counts, we compared two techniques: i) the classical method using the Nageotte haemocytometer; and ii) fluorescent staining with propidium iodide (PI). We performed these two techniques to evaluate the residual white cell count in 41 platelet units collected by cytapheresis. The difference in results obtained with the two techniques was borderline significant (P = 0.05). To evaluate the accuracy of both techniques, we added a known number of lymphocytes to platelet concentrates that had been filtered three times. There was a good correlation between the values obtained using the two techniques (r > 0.99). However, though the difference between the known value and PI results was not significant, the difference for Nageotte cell counter results was significant (P < 0.0001). From a practical point of view, the PI fluorescent technique is simple, rapid, and easy to carry out. Our results demonstrate the reliability of the PI technique for the evaluation of residual leukocytes.

Blood Platelets↗
PubMed1992

von Willebrand factor bound to glycoprotein Ib is cleared from the platelet surface after platelet activation by thrombin.

We recently reported that after activation of human platelets by thrombin, glycoprotein (GP) Ib-IX complexes are translocated to the surface-connected canalicular system (SCCS) (Blood 76:1503, 1990). As GPIb is a major receptor for von Willebrand factor (vWF) in platelet adhesion, we have now examined the consequences of thrombin activation on the organization of vWF bound to GPIb on the platelet surface. Studies were performed using monoclonal or polyclonal antibodies in either immunogold staining and electron microscopy (Au-EM) or in flow cytometry. When unstirred platelet-rich plasma was incubated with ristocetin, bound vWF was located by Au-EM as discrete masses regularly distributed over the cell surface. Platelets from a patient with Glanzmann's thrombasthenia, lacking GPIIb-IIIa complexes, gave a similar pattern, confirming that this represented binding to GPIb. That ristocetin was not precipitating vWF before their binding to the platelets was shown by the detection of similar masses on the surface of platelets of a patient with type IIB von Willebrand disease. Experiments were continued using washed normal platelets incubated in Tyrode-EDTA, the purpose of the EDTA being to limit the surface expression of endogenous vWF after platelet stimulation. Under these conditions, platelets were treated with ristocetin for 5 minutes at 37 degrees C in the presence of increasing amounts of purified vWF. This was followed by incubation with thrombin (0.5 U/mL) for periods of up to 10 minutes. Flow cytometry showed a time-dependent loss in the surface expression of vWF bound to GPIb and these changes were confirmed by Au-EM. In particular, immunogold staining performed on ultrathin sections showed that the bulk of the vWF was being cleared to internal membrane systems. Surface clearance of vWF during thrombin-induced platelet activation is a potential mechanism for regulating platelet adhesivity.

Antibodies↗
PubMed1992

Virus inactivation of fresh frozen plasma by a solvent detergent procedure: biological results.

In order to increase the safety of blood products, we have developed a procedure for the virus inactivation of fresh frozen plasma. Several batches have been prepared and with the first 10 batches, each of them composed of 60 litres of plasma, we have determined a set of biological parameters. Virus inactivation was realised using TnBP (1%) and Octoxynol 9 (1%). After their elimination with castor oil using chromatography on insolubilized C18 resin, glycine was added and the pH of the plasma was adjusted to 7.4. Plastic bags were aseptically filled with a mean volume of 200 ml of plasma. The mean levels of coagulation factors were all over 0.7 U/ml and their recovery from initial plasma was nearly the same as total protein except for factor VIII:C. The net loss in factor VIII:C was 16%, when including the dilution of plasma. In vivo and in vitro tests demonstrated that in the final product there were no activated factors. As in fresh frozen plasma, the protein concentration was over 50 g/l and the potassium level lower than 5 mmol/l. According to these results, virus-inactivated plasma has the same qualities of fresh frozen plasma and could now replace it.

Blood Coagulation Factors↗
PubMed1992

Further evidence that heparin-dependent thrombocytopenia may result from Fc receptor-mediated interactions.

Heparin-dependent thrombocytopenia (HDT) and associated thrombotic complications, are thought to be linked to the appearance of anti-platelet antibodies. Attempts were made to characterize the antibodies in the sera from 10 such patients. Western blotting against platelet antigens was inconclusive, often revealing multiple bands but with considerable variability from patient to patient. An often seen band of approximately 83 kDa was also given by some nonimmune sera and the antigen appeared to be predominantly intracellular in origin. Antibodies to major membrane glycoproteins were not readily apparent. This was confirmed by the MAIPA ("Monoclonal Antibody Immobilization of Platelet Antigens") test, performed to detect antibodies to GP Ib-IX and GP IIb-IIIa. Only one weak activity to GP Ib-IX and one weak activity to GP IIb-IIIa were detected. In contrast, an antibody to the PlA1 alloantigen was readily detected in the serum of an additional patient. The ability of HDT serum to induce the aggregation of control platelets was studied in detail. Aggregation was inhibited by EDU-3, a monoclonal antibody to GP IIb-IIIa complexes, and by the synthetic peptide RGDS, suggesting an involvement of the same pathway as used by physiologic agonists. However, in agreement with Chong et al (Thromb Res 55:291, 1989), we observed that aggregation was inhibited by rabbit IgG, suggesting that it was Fc-receptor mediated. Interestingly, 2E1, a monoclonal antibody to the Fc gamma RII receptor, induced platelet aggregation with a lag phase, a characteristic of HD antibodies. Nonetheless, for different donors, there was no correlation between the length of the lag phase induced by 2E1 and HD antibodies. Fc-receptor blockade should be considered as a means for diminishing the clinical complications of HDT.

Adult↗
PubMed1991

[Use of homologous erythrocyte concentrates. Analysis of economical factors].

The factors involved in reducing consumption of bank packed red cells (PRC) were studied over three one year periods (1983, 1987 and 1989) in a Department of Vascular and General Surgery. The effects of autologous blood salvage (started in 1987), associated with the management of homologous blood by a branch of the blood bank inside the operating theater suite were assessed. In 1989, intentional normovolaemic haemodilution became virtually systematic, on top of the intraoperative blood salvage, for all patients due to undergo surgery with a risk of severe blood loss. The number of surgical procedures carried out during those three years did not vary. However, in the same time, the annual consumption of homologous PRC decreased by an overall 56% (36.7% between 1983 and 1987, and 29.8% between 1987 and 1989). This decrease was mostly due to a fall in prescription in the operating theaters, and not in the wards. In the same time, albumin consumption increased sixfold. Such transfusional policies can only be carried out if there is good cooperation between the blood bank and the prescribers of blood products.

Blood Banks↗
PubMed1991

[Technique for automating HLA-DR typing].

Two types of anti-class II coated magnetic beads were compared for the use in isolation of B lymphocytes from whole blood. The HLA DR typing was performed in parallel after separation of the cells by the rosette technique. The depletion was monitored by Flow cytometry using CD2 and CD20 antibodies. Typing was performed using classic lymphocytotoxicity test of Propidium-Iodide-Carboxyfluorescein diacetate fluorescence. The results were scored with an ordinary microscope or by photometric evaluation. These techniques lead to simplification in cell isolation from small amounts of blood with an important gain of time and a less subjective interpretation of DR phenotyping was until now long and difficult.

Antigens, CD↗
PubMed1991

The influence of cryopreservation on activity and surface markers of lymphokine-activated killer cells.

Ficoll-separated and monocyte-depleted mononuclear cells isolated from normal leukapheresis products were cryopreserved. These cells were incubated with or without 1,000 U/ml of recombinant interleukin-2 (rIL-2) for 4 days, and their lymphokine-activated killer (LAK) and natural killer (NK) activities were measured. IL-2 activation induced a significant increase in the expression of the CD25 antigen. There was no change in CD2, CD3, CD4, CD8, CD16, CD56 and CD57 cell marker expression. Cryopreservation did not induce any change in the membrane antigen expression and in the lymphocyte subsets. The NK activity was well preserved and the decrease of LAK activity of IL-2-activated cells after cryopreservation was not significant. In contrast, cells activated before cryopreservation had a significantly lower cytotoxic activity and the number of cells expressing the IL-2 receptor was also significantly reduced. However, the decrease of CD56 expression was not significant. CD25 expression seemed to be proportional to the LAK activity of the cells. This study demonstrated that cryopreserved lymphocytes, after 4 days of culture with rIL-2, could be as active and could express the CD25 and CD56 cell surface markers in the same manner as fresh LAK cells.

Antigens, CD↗
PubMed1991

Polyreactivity of human monoclonal antibodies: human anti-Rh monoclonal antibodies of IgM isotype are frequently polyreactive.

The specific aim of this study was to characterize human anti-Rh monoclonal antibodies cross-reacting with self-antigens. We studied supernatants from man-mouse hybridomas and from lymphoblastoid cell lines. Man-mouse hybridomas were established by fusion of peripheral blood lymphocytes from healthy individuals recently immunized against Rh alloantigens, with mouse myeloma (or man-mouse heteromyeloma) cell lines. Lymphoblastoid cell lines were produced by Epstein-Barr virus induction of lymphocytes from identical sources. Of the 55 monoclonal alloantibodies studied, 11 also reacted with intracellular self-antigens as demonstrated by immunofluorescence assay on cryostat sections of human tissues. This cross-reactivity was mainly a property of monoclonal alloantibodies belonging to the IgM isotype (among the 11 cross-reacting mAbs 10 were IgM). The cross-reactivities of these monoclonal antibodies were ascertained by absorption of alloreacting antibodies with red blood cells. Similar results were obtained on a panel of purified cellular antigens by ELISA. The results confirm that during an immune response against a foreign antigen (alloantigen), B cells that produce polyreactive antibodies are not excluded from the pool of responding cells. Therefore, polyreactive autoantibodies present in sera from healthy individuals may be the result of an immune response against foreign antigens.

Antibodies, Monoclonal↗
PubMed1990

Lymphocyte immunization generates immunosuppressive factors in women with recurrent abortions.

Women with recurrent spontaneous abortions of unknown etiology were treated with injection of their partner's lymphocytes. The effect of lymphocyte immunization is evaluated by various immunological tests. The results demonstrate the appearance of immunosuppressive factors, especially P4 protein, present in normal pregnancy, which inhibits cellular cytotoxicity.

Abortion, Habitual↗
PubMed1989

[Indications for blood products].

The indications of blood products are now well established, and the optimal use of these products requires a perfect knowledge of both their characteristics and the risks created by their transfusion to patients. The description, since 1982, of HIV infection following the administration of blood components and plasma derivatives has prompted important modifications in the use of blood products, especially in intensive care units. At the moment, diluted albumin must be preferred to fresh frozen plasma, except in very special and rare cases. Modern viral inactivation techniques have made the haemostatic blood components quite safe as regards the transmission of viral diseases.

Blood Banks↗
PubMed1989

[Autograft of blood stem cells].

Autologous blood stem cell transplantation (ABSCT) is a new technique which has been increasingly used in recent years. It is now well established that ABSCT can be performed as safely as autologous bone marrow transplantation (ABMT) when high numbers of hemopoietic precursors are infused. Multiple leukophoreses are performed during marrow regeneration following chemotherapy-induced aplasia. Hemopoietic recovery (predominantly the granulocytic series) is probably faster after ABSCT than after ABMT. Among other advantages there may be minimal contamination by residual tumor cells in buffy-coats; however, this has not been fully investigated.

Hematologic Diseases↗
PubMed1989

[Identification of HLA B27 antigen by flow cytometry].

Cytofluorograph analysis after immunofluorescence with monoclonal antibodies can be useful for various antigens identification on the surface of cell membrane. This technic is described for antigen HLA B27 identification. This HLA antigen is known indeed to be linked to rhumatismal diseases. The fluorescence histograms obtained, allow to differentiate easily subjects which have HLA B27 phenotype and subjects which are HLA cross linked.

Antibodies, Monoclonal↗
PubMed1988

[Circulating hematopoietic cells. Results of 6 autologous grafts].

Six patients with acute non-lymphocytic leukemia underwent autologous transplantation of circulating stem cells collected during remission. They were given cyclophosphamide (120 mg/kg) and total body irradiation (1,000-1,200 rads) (five patients) or busulfan (16 mg/kg) and melphalan (140 mg/m2) before the transfusion of 6.7 X 10(8) nucleated cells/kg corresponding to 19.7 X 10(4) CFU-GM/kg. Granulopoietic engraftment was observed in every case and was influenced by the number of CFU-GM injected. Megakaryocytic recovery was obtained in four cases.

Acute Disease↗