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Biomedical subjects

D Blanchard

Publications and source records attributed to D Blanchard.

At least 19 recordsLinked to original sources
PubMed1995

Purification and partial characterization of the erythrocyte Kx protein deficient in McLeod patients.

A 37-kDa protein was immunopurified from human erythrocytes as a complex with a monoclonal antibody directed against the Kell blood group protein of 93 kDa. A rabbit antibody raised against the purified complex reacted on a Western blot with the 93-kDa and 37-kDa proteins and was able to immunoprecipitate the 37-kDa component from K0 erythrocytes which express large amount of the Kx antigen, but not from erythrocytes of patients suffering from McLeod syndrome, a X-linked disorder in which the Kx antigen is lacking. Additional studies have shown that the 37-kDa protein is not glycosylated, and permitted the sequence of the 22 first N-terminal amino acids to be established. This sequence was identical to the predicted protein product of the XK gene cloned recently, which is deleted or mutated in McLeod patients [Ho, M., Chelly, J., Carter, N., Danek, A., Crocker, P. & Monaco, A. P. (1994) Cell 77, 869-880]. Our findings provide strong evidence that the 37-kDa red cell membrane protein is identical to the Kx protein produced by the XK structural gene and demonstrate that Kx and Kell proteins are two subunits expressed as a complex hold by disulfide bond(s) at the red cell surface.

Amino Acid Sequence↗
PubMed1995

CD40 ligand-positive CD8+ T cell clones allow B cell growth and differentiation.

A fraction of activated CD8+ T cells expresses CD40 ligand (CD40L), a molecule that plays a key role in T cell-dependent B cell stimulation. CD8+ T cell clones were examined for CD40L expression and for their capacity to allow the growth and differentiation of B cells, upon activation with immobilized anti-CD3. According to CD40L expression, CD8+ clones could be grouped into three subsets. CD8+ T cell clones expressing high levels of CD40L (> or = 80% CD40L+ cells) were equivalent to CD4+ T cell clones with regard to induction of tonsil B cell proliferation and immunoglobulin (Ig) production, provided the combination of interleukin (IL)-2 and IL-10 was added to cultures. CD8+ T cell clones, with intermediate levels of CD40L expression (10 to 30% CD40L+ cells), also stimulated B cell proliferation and Ig secretion with IL-2 and IL-10. B cell responses induced by these CD8+ T cell clones were neutralized by blocking monoclonal antibodies specific for either CD40L or CD40. By contrast, CD40L- T cell clones (< or = 5% CD40L+ cells), only induced marginal B cell responses even with IL-2 and IL-10. All three clone types were able to activate B cells as shown by up-regulation of CD25, CD80 and CD86 expression. A neutralizing anti-CD40L antibody indicated that T cell-dependent B cell activation was only partly dependent on CD40-CD40L interaction. These CD40L- clones had no inhibitory effects on B cell proliferation induced by CD40L-expressing CD8+ T cell clones. Taken together, these results indicate that CD8+ T cells can induce B cell growth and differentiation in a CD40L-CD40-dependent fashion.

Animals↗
PubMed1995

Pope John XXI, ophthalmologist.

Pope John XXI was an ophthalmologist before becoming Pope. He was born in Lisbon and trained at University of Paris and was part of the early medical school faculty in Siena. He became physician for Pope Gregory X and shifted to church duties. He rose quickly in the ranks of the Catholic church and was elected Pope in 1276 AD. His term was short. He died when construction in the Papal Palace at Viterbo, collapsed on him. His text book is in two parts with introductions to the eye followed by descriptions of diseases with their mostly medical treatments. He concludes with a section about his own wonderful waters. The work survived and a copy was even found amongst Michelangelo's papers. Unfortunately the book turns out to be a plagiarism of two earlier text books. His most notable achievement supposedly was discovering that glaucoma was a disease with a hard eye. It turns out that this section is referring only to a suppurative external disease with indurated lids called sclerophthalmia.

Catholicism↗
PubMed1995

Immunological characterization of antigenic domains on human IL-2 receptor beta subunit: epitope-function relationships.

Five mAb directed at the IL-2R beta chain were analyzed for their binding and functional properties. They define three epitopes on a recombinant soluble beta chain or on the beta chain expressed at the surface of YT-2C2 cells. Epitope 1 (A41 and 6E8 mAb) is part of the IL-2 binding domain, whereas epitope 2 (CF1 and 6E10 mAb) is not involved in IL-2 binding. Epitope 3 (6B5 mAb) also partly overlaps the IL-2 binding domain but does not overlap epitopes 1 and 2. None of the mAb can by themselves inhibit IL-2 induced proliferation of a human activated T cell clone. Only epitope 1 mAb can synergize with an anti-alpha chain mAb to inhibit this proliferation. Using epitope 1 and 2 mAb as well as a purified, recombinant form of the IL-2R beta chain extracellular domain, an ELISA-based immunoassay was set up which allows the quantitative determination of soluble and detergent solubilized IL-2R beta chains. Epitopes 1 and 2 are in non-competitive interaction: the binding of a mAb to one epitope decreases the affinity of a mAb for the second epitope. Epitope 2 mAb have binding stoichiometries (approximately 16,000 sites/cell) which are approximately 80% higher than that of epitope 1 mAb and IL-2 itself (approximately 9000 sites/cell). Upon binding of epitope 2 mAb, the stoichiometries of epitope 1 mAb and IL-2 are increased to reach the stoichiometry of epitope 2 mAb.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1995

Minimally differentiated erythroleukaemia (AML M6 'variant'): a rare subset of AML distinct from AML M6. Groupe Français d'Hématologie Cellulaire.

We describe eight cases of erythroleukaemia distinct from FAB-AML M6, which demonstrate minimal erythroid differentiation not associated with a myeloblastic component. Three infants (including a Down's syndrome) and two adults presented with a de novo leukaemia. One case was preceded by an untreated refractory anaemia with excess of blasts and one by polycythaemia vera. One case presented with an inaugural blast crisis of chronic myeloid leukaemia. In four patients the leukaemic cells showed a proerythroblast-like morphology. The four other were initially classified as undifferentiated AL (two cases) or AML MO (two cases) because of the immature aspect of the cells, their lack of myeloperoxidase activity and the absence of B, T lymphoid and myeloid (My) marker expressions apart from the CD33 antigen. Immunophenotyping in three cases showed an immature erythroblast profile (glycophorins A and B+, spectrin+). In the five others the erythroid nature was recognized by the expression of ABH blood group system on fresh cells (four cases) and glycophorin A on cells after 3 d in vitro culture with erythropoietin (EPO) + IL3 (two cases). Moreover, an erythroid colony growth of leukaemic origin was observed in three patients. In conclusion, the study of erythroid marker expression is of particular importance when immunophenotyping leukaemic cells with a proerythroblast-like morphology or an undifferentiated aspect and a HLA DR-, CD36++, B-, T-, My- (CD33 +/-) phenotype. We propose the term AML M6 'variant' for this rare type of AML.

Aged↗
PubMed1995

Flow cytometry analysis of dual red blood cell populations after bone marrow transplantation.

Flow cytometry represents an alternative method to agglutination assays for the accurate quantification of mixed field populations of erythrocytes observed after bone marrow transplantation. Murine monoclonal antibodies directed against the blood group ABH antigens were selected and processed in order to prepare ready-to-use fluorescent reagents. Anti-A (NaM87-1F6; IgG3), anti-B (NaM9-2E11; IgG3) and anti-H (NaM19-7E11; IgM) were purified, labelled with fluorescein isothiocyanate, and used in a direct flow cytometry assay. Anti-A1 (NaM1-1C9; IgG3) was no longer active after FITC-labelling and then was used in an indirect assay. The agglutination was prevented by formaldehyde pretreatment of erythrocytes. Using artificially-made double populations of erythrocytes, measured values with mixtures of 1-100% of cells were very closely related to expected values, showing both the sensitivity and the accuracy of the method. From careful investigation of a series of bone-marrow transplanted patients, we conclude that engraftments could be demonstrated earlier by flow cytometry than by agglutination, because minor populations (1-10%) of cells could be determined accurately only with labelled reagents. In addition, the disappearance of the donor cells on a long-term follow-up of patients enabled an earlier detection of graft failure in one case. The proposed method provides appreciable help to follow engraftment in patients and may have more general applications for the study of other haemopoietic chimaeras.

ABO Blood-Group System↗
PubMed1995

CD40-activated human naive surface IgD+ B cells produce IgG2 in response to activated T-cell supernatant.

Human IgG2 is an isotype associated with immune responses to carbohydrates. While interleukin-10 (IL-10) induced CD40-activated naive surface (s)IgD+ human B cells to secrete IgG1 and IgG3, none of 20 recombinant cytokines tested alone, or in combination with IL-10, was able to induce these cells to produce IgG2. This was not due to a specific inability of these sIgD+ B cells, as they could be induced to secrete microgram amounts of IgG2, as well as the three other IgG subclasses, when cultured with an anti-CD3-activated CD4+ T-cell clone. The supernatant of this activated CD4+ T-cell clone contained a soluble factor(s) able to induce the secretion of IgG2 by CD40-activated sIgD+ B cells. Following activation, blood T cells also produced a factor(s) inducing CD40-activated naive B cells to secrete IgG2. This CD4+ T-cell clone will thus permit us ultimately to define the presently uncharacterized cytokine(s) inducing naive B cells to secrete IgG2. This will provide a new insight for the study of immunodeficiencies involving a selective defect in IgG2.

B-Lymphocytes↗
PubMed1994

Protection of rat endothelial cells from primate complement-mediated lysis by expression of human CD59 and/or decay-accelerating factor.

The present study analyzed the ability of human decay-accelerating factor (DAF) and CD59 to protect rat endothelial cell (EC) clones from human and primate complement-mediated lysis. By flow cytometry and Scatchard analysis, we show that human DAF and/or CD59 cDNAs under the transcriptional control of elongation factor 1-alpha promoter were expressed at levels similar to or higher than that of a human EC line. Human DAF and CD59 were released from the surface of transfected rat cells by phosphatidylinositol phospholipase C, demonstrating that the two molecules were linked to the cell membrane by means of a glycolipid anchor. The functional activity of the two human C regulatory proteins expressed on rat EC lines was studied using an in vitro assay of C-dependent cytotoxic in which rat EC were incubated with human or nonhuman primate sera as sources of xenogeneic natural antibodies and C. We demonstrate that human and monkey xenogeneic natural antibodies bind to rat cells and induce lysis by a C-dependent mechanism involving mainly the C direct activation pathway. Our data indicate that human DAF and CD59, expressed either alone or in combination, abrogated all EC cytotoxicity, even in the presence of 50% human serum. This protective phenotype was correlated with decreased membrane attack complex (CD59 and/or DAF transfectants) and C3 deposition (DAF transfectants) on EC surface. Antibodies against the transfected molecules abolished the protection against C-mediated lysis.

Animals↗
PubMed1994

Variation in fetal hemoglobin parameters and predicted hemoglobin S polymerization in sickle cell children in the first two years of life: Parisian Prospective Study on Sickle Cell Disease.

Intracellular hemoglobin S (HbS) polymerization is most likely to be the primary determinant of the clinical and biologic manifestations of sickle cell disease (SCD). Fetal hemoglobin (HbF) does not enter the HbS polymer and its intracellular expression in sickle erythrocytes inhibits polymerization. HbF levels, high at birth but decreasing thereafter, protect the newborn from the clinical manifestations of this hemoglobinopathy. We have measured the sequential changes in HbF, F reticulocytes, and F cells in the first 2 years of life in 25 children with SCD and compared the results with those obtained in 30 normal children (AA). We have also calculated HbF per F cell (F/F cell), the preferential survival of F cells versus non-F cells, as measured by the ratio F cells versus F reticulocytes (FC/FR) and polymer tendency at 40% and 70% oxygen saturation. HbF levels decreased from about 80.4% +/- 4.0% at birth to 9.2% +/- 2.9% at 24 months. During this time, we observed a regular decrease of the F reticulocytes and the F cells. The kinetics of the decline of F/F cell was comparable with the decline of HbF, rapid from birth (mean, 27.0 +/- 3.6 pg) to 12 months of age (mean, 8.5 +/- 1.5 pg) and then slower from 12 to 24 months of age (mean, 6.2 +/- 1.0 pg) in the SCD children. In the AA children, the decrease in HbF, due to changes in both numbers of F cells and F/F cell, was more precipitous, reaching steady-state levels by 10 months of age. Calculated values for mean polymer tendency in the F-cell population showed that polymerization should begin to occur at 40% oxygen saturation at about 3 months and increase progressively with age, whereas polymerization at 70% oxygen saturation would not occur until about 24 months. These values correspond to HbF levels of 50.8% +/- 10.8% and 9.2% +/- 2.9%, respectively, and F/F cell levels of 15.6 +/- 4.5 pg and 6.2 +/- 1.0 pg, respectively. In the non--F-cell population, polymerization was expected at birth at both oxygen saturation values. Three individuals had significantly greater predicted polymerization tendency than the remainder of the group because of early decreases in HbF. These individuals in particular, the remainder of the cohort, as well as other recruited newborns, will be studied prospectively to ascertain the relationship among hematologic parameters, which determine polymerization tendency and the various clinical manifestations of SCD.

Anemia, Sickle Cell↗
PubMed1994

Human natural antibodies to porcine platelets.

The specificity of human natural antibodies directed against blood cells from pigs was investigated by ELISA and immunoblotting. Both IgG and IgM were identified as xenoantibodies reacting with pig platelets adsorbed to microplates. The antibodies could be absorbed on platelets as well as on RBC, suggesting that the corresponding antigens are expressed on the surface of a variety of cells. Galactose (20 mM) and melibiose (10 mM) partially inhibited (approximately 50%) the binding of antibodies to platelets, whereas lactose and cellobiose (300 mM) did not. On immunoblots, platelet glycoproteins of 115, 125, 135, 180, and 210 kDa were specifically revealed with human sera diluted 1/20. In contrast with the results obtained by ELISA, xenoantibodies reactive with blotted glycoproteins were of the IgM class and the binding was not significantly inhibited by galactose or melibiose. "Anti-Gal" antibodies, purified from human sera by affinity chromatography on a melibiose-Sepharose immunoabsorbent, represented only a minor portion of the antibodies reactive with porcine platelets. Purified anti-Gal antibodies bound to the 115- and 135-kDa components, whereas the antibodies in the nonretained fraction revealed the 125-kDa molecule. As deduced from these data, human serum contains natural antibodies of both IgG and IgM classes directed to several porcine antigens. Gal-reactive structures were identified on the 115- and 135-kDa platelet glycoproteins, which might be homologous to their counterpart on endothelial cells. Also, the present work suggests that a majority of the natural antibodies reacted with other unidentified structures.

Animals↗
PubMed1994

Activated CD4+ T cells induce CD40-dependent proliferation of human B cell precursors.

Anti-CD3-activated human CD4+ T cell clones were found to induce proliferation of CD10+, CD19+, surface(s) Ig- B cell precursors (BCP) isolated from human fetal bone marrow. The great majority of the B lineage cells recovered in cocultures of BCP and activated T cells displayed a BCP phenotype (Ig- or cytoplasmic mu+ and kappa/lambda-), including most of the cycling cells, indicating that the cultures do not favor a transition to mature B cells. Supernatants of activated T cells were ineffective in inducing BCP proliferation, indicating the necessity of close association with stimulator cells. In line with this finding, the CD40 molecule was found to represent an important component of the cocultures, as BCP proliferation was strongly inhibited by soluble anti-CD40 antibody. In addition, CD4+ T cell clones from a hyper-IgM patient expressing a truncated CD40 ligand (CD40-L) failed to induce BCP proliferation. Finally, a combination of cytokines (IL-2, IL-3, IL-7, and IL-10) enhanced the observed T cell-dependent BCP proliferation, but could not substitute for the deficient CD40-L. Taken together, our data demonstrate that CD4+ T cells exert a stimulatory effect on in vitro B human lymphopoiesis via the CD40 pathway. The present results suggest that T cells may play an important role in regulating B cell ontogeny in the bone marrow.

Antigens, CD↗
PubMed1994

Role of CD40 antigen and interleukin-2 in T cell-dependent human B lymphocyte growth.

In the present study, we examined the participation of CD40 ligand (L)-CD40 interaction in T cell-dependent B cell responses. To this end, purified B lymphocytes were cultured over irradiated CD4+ cloned T cells activated with immobilized anti-CD3 antibody. The anti-CD40 mAb 89 strongly blocked, in a specific fashion, both proliferation and Ig secretion of tonsil B cells. Interestingly, proliferation of surface (s)IgD+ B cell was significantly less inhibited by anti-CD40 than that of sIgD- cells. Preactivated T cells induced B cells to grow and secrete immunoglobulins preferentially in response to IL-2. This contrasts with the CD40 system where B cells are essentially responsive to IL-4 and IL-10 but not to IL-2 alone. Collectively, these data indicate that CD40L-CD40 interaction plays an important role in IL-2 mediated T cell-dependent B cell responses. However, the activation of a subset of sIgD+ cells may be independent of this interaction.

Antigens, CD↗
PubMed1994

B cells regulate expression of CD40 ligand on activated T cells by lowering the mRNA level and through the release of soluble CD40.

The expression of CD40 ligand (CD40L) on activated T cells (CD4+ T cell clone MT9) is diminished when the T cells are cultured in the presence of B cells. This effect, observed both with normal tonsil B cells and with the B cell line JY, was detected after 6 h and sustained at least until 18 h of co-culture. Analysis of mRNA showed that CD40L mRNA levels were not modified after 6 h, but were significantly down-regulated after 18 h of co-culture with B cells. Although CD40L expression could not be detected by a CD40-Fc chimera, the molecule was still expressed at the membrane as shown with a polyclonal antiserum against CD40L (anti-TRAP). In addition, T cells activated in the presence of B cells were stained by a polyclonal antiserum against CD40, without the appearance of CD40 mRNA. These results indicated that a soluble form of CD40 (sCD40) bound to the expressed CD40L on T cells. The existence of sCD40 was confirmed by detection of sCD40 in B cell supernatants using a specific enzyme-linked immunosorbent assay. Collectively, these data show that B cells can regulate the expression of CD40L on activated T cells at least by two different mechanisms.

Antigens, CD↗
PubMed1994

Influence of the size of the polar head of non-ionic detergents on membrane proteins immunoaffinity purification.

Nonionic polyoxyethylene type detergents (CxEy) are widely used to solubilize and purify membrane proteins. The detergent hydrophobic moiety (Cx) replaces phospholipids at exposed hydrophobic regions of the membrane proteins. During chromatography on an immobilized anti-Kell antibody to purify Kell protein (an integral erythrocyte protein), it was observed that the size of the polar head of an non ionic detergent added to the mobile phase appeared to influence the interaction of the detergent-protein complex with the immobilized antibody. Further studies were performed using another erythrocyte membrane protein, Glycophorin C and three anti-GPC monoclonal antibodies directed against three epitopes of the extracytoplasmic domain of the protein. The interaction of GPC with the three Protein A-coupled monoclonal antibodies was studied in the presence of three detergents C12E<9>, C13E<15> and C12E<23>. It was observed in batch mode and in column chromatography experiments that the adsorption of GPC to the immunoaffinity supports decreased as the size of the detergent polar head increased. Thus, the polyoxyethylene chain of a detergent might prevent the interaction of the detergent-protein complex with the immobilized antibody.

Animals↗
PubMed1994

Serological analysis by A60 antigen ELISA and BCG immunoblotting in domestic carnivores experimentally vaccinated with mycobacterium bovis BCG.

The serological response to Mycobacterium bovis BCG vaccination was studied in 3 cats, 3 dogs and 3 puppies. The animals received two doses of 0.1 mg of BCG and were studied over a period of 8 months simultaneously by ELISA with antigen A60 (Anda Biologicals, Strasbourg, France) and immunoblotting with BCG. The two methods detected an increase of antibodies at 3 or 5 weeks. In the cats, specific antibody titer remained high and stable for more than one year, in the dogs they diminished quickly within 23 weeks. Carnivores elicit a serological response against specific protein antigens in the bands corresponding to 18 and 25kDa, 30 and 45kDa, and especially 35 and 42kDa bands, and to minor bands at higher molecular weight. Non-specific bands at 50-55 kDa and 70 kDa, assigned to heat shock proteins, were enhanced by BCG vaccination. Cat immunosera recognized on A60 immunoblots the specific homologous bands at 20-25 kDa and 32 kDa, but also two other dominant bands: one was partially specific (65 kDa) and the other was absent from the M. bovis and M. paratuberculosis profiles. The suitability of A60 ELISA for detection of mycobacterial infection in carnivores may be highlighted by immunoblot analysis.

Animals↗