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L Boumsell

Publications and source records attributed to L Boumsell.

At least 55 records · Page 3Linked to original sources
PubMed1996

CD100 is associated with CD45 at the surface of human T lymphocytes. Role in T cell homotypic adhesion.

CD100 is a 150-kDa human surface glycoprotein implicated in T cell activation. Using BB18 and BD16 mAbs to two discrete epitopes of the CD100 molecule, we have shown previously that triggering the CD100 molecule through the BB18 epitope is comitogenic with PMA, whereas it lacks a detectable effect on CD2- and CD3-induced PBMC proliferation. Conversely, triggering the CD100 molecule through the BD16-defined epitope only exerts an effect on CD2- and CD3-induced PBMC proliferation. In the present study, we investigated the molecular relationship between CD100 and another surface structure involved in human T cell proliferation, the CD45 phosphatase. We show in this study that CD100 is associated with CD45 and that this association has functional significance. The association was demonstrated using coimmunoprecipitation and detection of CD45 enzymatic PTPase activity. Furthermore, we show that the association is increased during T cell activation and that triggering CD45 molecules through discrete epitopes induces the down-modulation of CD100 molecules at the cell surface. Interestingly, we demonstrate that this modulation could be attributed to the shedding of a soluble form of CD100 in the culture supernatant. Finally, one of the functional consequences of this T cell activation-induced CD100-CD45 association is revealed by the finding that CD100 mAbs have an effect on CD45-induced T cell aggregation.

Antibodies, Monoclonal↗
PubMed1996

Human CD100, a novel leukocyte semaphorin that promotes B-cell aggregation and differentiation.

Herein we describe the molecular characterization of the human leukocyte activation antigen CD100 and identify it as the first semaphorin, to our knowledge, in the immune system. Semaphorins have recently been described as neuronal chemorepellants that direct pioneering neurons during nervous system development. In this study we demonstrate that CD100 induces B cells to aggregate and improves their viability in vitro. We show that CD100 modifies CD40-CD40L B-cell signaling by augmenting B-cell aggregation and survival and down-regulating CD23 expression. Thus, these results suggest that semaphorins as exemplified by CD100 also play a functional role in the immune system.

Amino Acid Sequence↗
PubMed1996

Enhanced CD3 monoclonal antibody induced proliferation of colonic mucosal T lymphocytes in Crohn's disease patients free of corticosteroid or immunosuppressor treatment.

Mucosal lymphocytes are increasingly activated in Crohn's disease. In order to investigate this phenomenon we tested the response of cultured colonic mucosal T lymphocytes to CD3 activation. These lymphocytes were obtained by biopsy from control subjects and Crohn's disease patients. T cells from mucosa involved in Crohn's disease showed a higher CD3-induced proliferative response compared to control T lymphocytes (P < 0.01). T cells from uninvolved areas showed a wide range of response, ranging from normal to very high proliferative indices. Our results suggest that the exaggerated response of mucosal T lymphocytes, due to the impairment of the downregulation of the CD3-dependent signaling process, may contribute to the pathogenesis of Crohn's disease.

Adult↗
PubMed1996

Lymphocytes subsets in normal individuals: analysis by four color immunofluorescence and flow cytometry on whole blood.

In order to precisely define human lymphocytes subsets, we used four color immunofluorescence analysis and flow cytometry. We report here the results of systematic studies performed on whole blood from 20 normal volunteers. This was performed using monoclonal antibodies recognizing 18 different CD molecules and analyzed here into 14 different 4-color immunofluorescence combinations. This showed that among T cells, the two major CD3+CD8+ and CD3+CD8- subsets differed greatly in the percentage of cells expressing CD26, CD27, CD28, CD38, CD45RA, CD45RO, CD57, S6F1, BY55, CD101 and their respective combination representing an array of subsets. Furthermore the minor NK subsets, i.e. CD2+CD3-CD8+, CD2-CD3-CD8+, CD2+CD3-CD8-, CD2-CD3-CD8- also differed in percentages of cells expressing CD16, CD56, CD57, S6F1, BY55 and their combinations.

Antigens, CD↗
PubMed1996

Functional role of PECAM-1/CD31 molecule expressed on human cord blood progenitors.

CD31/PECAM-1 (platelet endothelial cell adhesion molecule-1) is a 130 kDa integral membrane protein of the immunoglobulin gene superfamily with the distinctive feature of being expressed on several cell types associated with the vascular compartment. In the present study we report a novel, unique CD31 mAb termed IP28A which reacts with all CD34 molecule expressing hematopoietic progenitor cells and a subset of T, B and NK lymphocytes from human cord blood. Interestingly, we show that the number of CFU-GM and BFU-E was significantly augmented in cord blood progenitor cultures when purified IP28A mAb was added to rhSCF plus rhGM-CSF and rhEpo, respectively. Thus, these results are of relevance in the field of hematopoietic stem cell transplantation as they reveal an agonistic property of the IP28A/CD31 mAb on the differentiation of cord blood progenitor cells.

Animals↗
PubMed1995

Detection of membrane-bound HLA-G translated products with a specific monoclonal antibody.

A monomorphic anti-HLA-G monoclonal antibody (mAb) was obtained by immunization of HLA-B27/human beta 2-microglobulin double-transgenic mice with transfected murine L cells expressing both HLA-G and human beta 2-microglobulin. This mAb, designated BFL.1, specifically recognizes, by flow cytometry analysis, the immunizing HLA-G-expressing cells, whereas it does not bind to parental untransfected or to HLA-B7- and HLA-A3-transfected L cells, suggesting that it distinguishes between classical HLA-A and -B and nonclassical HLA-G class I molecules. This was further assessed by the absence of BFL.1 reactivity with a number of human cell lines known to express classical HLA class I proteins. In addition, we showed that the BFL.1 mAb also labels HLA-G-naturally-expressing JEG-3 and HLA-G-transfected JAR human choriocarcinoma cell lines as well as a subpopulation of first-trimester placental cytotrophoblast cells. Further biochemical studies were performed by immunoprecipitation of biotinylated membrane lysates: BFL.1, like the monomorphic W6/32 mAb, immunoprecipitated a 39-kDa protein in HLA-G-expressing cell lines, a size corresponding to the predicted full-length HLA-G1 isoform. However, in contrast to W6/32, which immunoprecipitates both classical and nonclassical HLA class I heavy chains, BFL.1 mAb does not recognize the class Ia products. Such a mAb should be a useful tool for analysis of HLA-G protein expression in various normal and pathological human tissues and for determination of the function(s) of translated HLA-G products.

Animals↗
PubMed1995

Activation signals are delivered through two distinct epitopes of CD100, a unique 150 kDa human lymphocyte surface structure previously defined by BB18 mAb.

We have previously reported the identification of a glycoprotein dimer, now termed CD100, at the lymphocyte cell surface using a mAb termed BB18. In the present study we isolated a second mAb, termed BD16, recognizing another epitope of this 150 kDa structure. We show that interaction with individual mAb triggers differential functional effects on peripheral blood lymphocytes (PBL) and purified T cells. In particular and of the utmost interest, BD16 mAb strongly inhibits CD3 induced PBL proliferation while it dramatically increases the CD2 induced proliferation. In contrast, after T cell purification, BD16 mAb increases both CD2 and CD3 induced proliferation. It has to be noted that perturbation of the same 150 kDa surface molecule with BB18 mAb exerts no effect on CD2 and CD3 induced proliferations, while inducing a strong lymphocyte proliferation in the presence of submitogenic concentrations of phorbol myristate acetate.

Antibodies, Monoclonal↗
PubMed1995

Langerhans' cell histiocytosis. Definitive diagnosis with the use of monoclonal antibody O10 on routinely paraffin-embedded samples.

The histological and immunohistochemical findings of 34 biopsy specimens from patients with Langerhans' cell histiocytosis (LCH) are reported, with special emphasis on the findings with CD1a mouse monoclonal antibody (MAb) O10 using paraffin-embedded material. Eighteen patients were treated in an adult hospital (mean age, 26.3 years), and the 16 others were children (mean age, 3 years) from a pediatric center. Specimens included 17 bone, 14 skin, two lung, and one lymph node. Tissue was fixed in formalin or Bouin's, and most bone samples were decalcified in nitric acid. Frozen sections were available for 16 cases and electron microscopy for one. Light microscopy was suggestive of LCH in all cases, characterized by large mononucleated cells with abundant eosinophilic cytoplasm and "coffee bean" nucleus. In 33 of the 34 paraffin-embedded LCH samples, mononucleate cells were stained by MAb O10. As controls, we investigated seven tumors expressing S-100 protein (three nevi, two melanomas, two neurofibromas): all were negative with MAb O10. Five non-Langerhans' cell histiocytoses (three juvenile xanthogranulomas and two Rosai-Dorfman lymphadenopathies) were also negative with MAb O10. The results show that in most cases a definitive diagnosis of LCH can be assessed on paraffin-embedded tissue specimens with the help of immunohistochemistry using MAb O10.

Adult↗
PubMed1995

Potential antileukemic effect of gamma delta T cells in acute lymphoblastic leukemia.

The immune response to leukemia is poorly understood. We postulated that nonmalignant T lymphocytes remaining within bone marrow from children with newly diagnosed ALL could be involved in this immune response. T lymphocytes which expressed gamma delta TCR comprised less than 1% of ALL marrow cells. A preferential outgrowth of gamma delta T cells within the CD3 population was observed when marrow cells were cultured with IL-2 alone or with stimulating feeder cells. These results, obtained in a series of 14 patients with precursor B-ALL, were significantly different when compared with expansions from normal marrow cells. In one patient, the clones established from the expanded population displayed different patterns of cytotoxicity against tumoral targets of the B cell lineage. Some clones expressing the TCR V delta 1 segment showed cytotoxic activity against a cell line derived from a pre-B ALL without activity against a LAK-sensitive B cell line. Using PCR amplification, one such clone was detected at high frequency, in the primary expansion of ALL marrow cells. These results suggest a prior activation in vivo of some gamma delta T cells by leukemic cells and provide some evidence on the role of these subsets in the immune response to leukemia.

Adolescent↗
PubMed1994

BY55 monoclonal antibody delineates within human cord blood and bone marrow lymphocytes distinct cell subsets mediating cytotoxic activity.

We had previously reported, using BY55 monoclonal antibody, a cell surface 80-kDa protein restricted to human functional peripheral blood cytotoxic lymphocytes with either natural killer CD3- or cytotoxic T lymphocyte CD3+CD8+ phenotype. In the present report, we studied the cytotoxic lymphocytes in adult bone marrow and newborn cord blood as these organs are commonly used as sources of hematological stem cells for allogeneic transplantation. Our results showed that BY55 mAb labeled only 5-10% of the bone marrow lymphocytes, which included a major proportion of CD3+ CD8+ cytotoxic T lymphocytes. Interestingly, within cord blood cells, BY55+ lymphocytes represented 20-35% of the lymphocytes corresponding exclusively to a CD3- cell subset. Furthermore, we detected in cord blood no cytotoxic T lymphocyte activity but we demonstrated that the CD3-BY55+ cell subset contained the whole natural killer activity.

Antibodies, Monoclonal↗
PubMed1994

CD antigens 1993.

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Antibodies, Monoclonal↗
PubMed1994

CD antigens 1993.

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Antigens, CD↗
PubMed1994

CD antigens 1993.

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Antigens, CD↗
PubMed1994

Differential proliferative responses in subsets of human CD28+ cells delineated by BB27 mAb.

We report the identification of a novel 140 kDa disulfide-linked dimer expressed by a subset of peripheral blood T lymphocytes. This molecule, which is recognized by mAb BB27, is also detected on cells of the myelomonocytic lineage. In the T cell lineage, its expression is positively modulated after lymphocyte activation. A series of double-labeling experiments revealed that BB27 mAb identifies new CD4 and CD8 cell subsets different from those defined by CD45RA, CD45RO, CD26, CD29, CD31, and CD38. Finally, BB27 mAb also subdivides the CD28 subset. Of the utmost interest is the finding that a proliferative response to CD28 mAb and phorbol myristate acetate stimulation is exclusively obtained in the CD28+BB27+ cell subset, whereas the CD28+BB27- subset fails to proliferate.

Animals↗
PubMed1994

Two subpopulations of human triple-negative thymic cells are susceptible to infection by human immunodeficiency virus type 1 in vitro.

Some infants infected with human immunodeficiency virus type 1 (HIV-1) rapidly develop a fatal disease characterized by a severe lymphopenia. To explain the immune dysfunction, we proposed a mechanism by which a nongeneration of CD4+ T cells is caused by HIV-1 infection of thymic cells. To examine this hypothesis, we infected primary triple-negative (TN; phenotypically CD3- CD4- CD8-), CD1a- TN, or CD1a+ TN thymic cell subsets. Our data indicate that by flow cytometry, TN, CD1a- TN, and CD1a+ TN cells remain CD4 negative throughout the culture period. We demonstrated that TN and CD1a+ TN thymic cell subsets are susceptible to HIV-1 as is the entire thymic cell population, whereas CD1a- TN cells are not. A limited number of infected TN cells are expressing HIV-1 but the level of transcription is very high in permissive cells, as detected by in situ hybridization. We then performed blocking experiments on TN cells to examine the mechanism of HIV-1 entry into these cells. CD4 (OKT4a) monoclonal antibody blocks their infection. Finally, infection experiments on two subpopulations of TN cells (CD2+ CD7+ and CD2- CD7-) indicate that infected TN cells may correspond to both immature thymocytes and thymic dendritic cells. These data are of particular interest since infection of thymic stromal cells might result in an impairment of T-cell differentiation, which may explain a nongeneration of functional CD4+ T-cell population in the thymus. This phenomenon may play a role in AIDS pathogenesis, in particular in infants born from seropositive mothers.

Antibodies, Monoclonal↗
PubMed1993

Tyrosine phosphorylation and association with phospholipase C gamma-1 of the GAP-associated 62-kD protein after CD2 stimulation of Jurkat T cell.

Numerous substrates are tyrosine phosphorylated upon CD2 stimulation of human Jurkat T cells using a mitogenic pair of CD2 monoclonal antibodies, including the phospholipase C (PLC)gamma-1-p35/36 complex. Most of these substrates are identically tyrosine phosphorylated after CD3 ligation, suggesting that both stimuli share the same biochemical pathway. We show, however, in this report that a 63-kD protein is specifically phosphorylated on tyrosine residues after ligation of the CD2 molecule. The tyrosine phosphorylation of p63 can be induced independently of other substrates when using a single CD2 mAb recognizing the D66 epitope of the molecule. Importantly, this CD2-induced tyrosine phosphorylation of p63 can also occur in the absence of the CD3 zeta chain membrane expression, and is also distinct from the protein tyrosine kinases p56lck and p59fyn. We demonstrate, moreover, that p63 is physically linked with PLC gamma-1 and p35/36 upon CD2 stimulation. Finally, we also show that a 62-kD protein coimmunoprecipitating with the p21ras GTPase activating protein (GAP) is heavily tyrosine phosphorylated only after CD2 stimulation. This ultimately suggests that p63 may represent in fact the 62-kD protein that associates with GAP after tyrosine phosphorylation. Taken together, these results demonstrate the occurrence in Jurkat cells of a tyrosine kinase pathway specifically coupled to the CD2 molecule. They also suggest a function of the p62-GAP-associated protein as a link between PLC gamma-1 and p21ras activation pathways after CD2 activation.

Antibodies, Monoclonal↗