Biomedical subjects

J Banchereau

Publications and source records attributed to J Banchereau.

At least 55 records · Page 3Linked to original sources

PubMed1998

The normal counterpart of IgD myeloma cells in germinal center displays extensively mutated IgVH gene, Cmu-Cdelta switch, and lambda light chain expression.

Human myeloma are incurable hematologic cancers of immunoglobulin-secreting plasma cells in bone marrow. Although malignant plasma cells can be almost eradicated from the patient's bone marrow by chemotherapy, drug-resistant myeloma precursor cells persist in an apparently cryptic compartment. Controversy exists as to whether myeloma precursor cells are hematopoietic stem cells, pre-B cells, germinal center (GC) B cells, circulating memory cells, or plasma blasts. This situation reflects what has been a general problem in cancer research for years: how to compare a tumor with its normal counterpart. Although several studies have demonstrated somatically mutated immunoglobulin variable region genes in multiple myeloma, it is unclear if myeloma cells are derived from GCs or post-GC memory B cells. Immunoglobulin (Ig)D-secreting myeloma have two unique immunoglobulin features, including a biased lambda light chain expression and a Cmu-Cdelta isotype switch. Using surface markers, we have previously isolated a population of surface IgM-IgD+CD38+ GC B cells that carry the most impressive somatic mutation in their IgV genes. Here we show that this population of GC B cells displays the two molecular features of IgD-secreting myeloma cells: a biased lambda light chain expression and a C&mu-Cdelta isotype switch. The demonstration of these peculiar GC B cells to differentiate into IgD-secreting plasma cells but not memory B cells both in vivo and in vitro suggests that IgD-secreting plasma and myeloma cells are derived from GCs.

B-Lymphocytes↗

PubMed1998

Dendritic cells and the control of immunity.

B and T lymphocytes are the mediators of immunity, but their function is under the control of dendritic cells. Dendritic cells in the periphery capture and process antigens, express lymphocyte co-stimulatory molecules, migrate to lymphoid organs and secrete cytokines to initiate immune responses. They not only activate lymphocytes, they also tolerize T cells to antigens that are innate to the body (self-antigens), thereby minimizing autoimmune reactions. Once a neglected cell type, dendritic cells can now be readily obtained in sufficient quantities to allow molecular and cell biological analysis. With knowledge comes the realization that these cells are a powerful tool for manipulating the immune system.

Animals↗

PubMed1998

Caspase-dependent ceramide production in Fas- and HLA class I-mediated peripheral T cell apoptosis.

We recently demonstrated that the engagement of HLA class I alpha1 domain induced Fas-independent apoptosis in human T and B lymphocytes. We analyzed the signaling pathway involved in HLA class I-mediated apoptosis in comparison with Fas (APO-1, CD95)-dependent apoptosis. The mouse mAb90 or the rat YTH862 monoclonal antibodies which bind the human HLA class I alpha1 domain induced the production of ceramide which was blocked by addition of the phosphatidylcholine-dependent phospholipase C inhibitor, D609. Furthermore, HLA class I-mediated apoptosis involved at least two different caspases, an interleukin-1 converting enzyme-like protease and another protease inhibited by the CPP32-like protease inhibitor Ac-DEVD-CHO. Despite similarity between Fas and HLA class I signaling pathways, we failed to demonstrate any physical association between these two molecules. We also report that the pan-caspase inhibitory peptide zVAD-fmk, but not Ac-DEVD-CHO and Ac-YVAD-CHO, inhibited decrease of mitochondrial transmembrane potential and generation of ceramide induced by anti-HLA class I and anti-Fas monoclonal antibodies, whereas all three peptides efficiently inhibited apoptosis. Altogether these results suggest that signaling through Fas and HLA class I involve caspase(s), targeted by zVAD-fmk, which act upstream of ceramide generation and mitochondrial events, whereas interleukin-1 converting enzyme-like and CPP32-like proteases act downstream of the mitochondria.

Amino Acid Chloromethyl Ketones↗

PubMed1998

The cytokine profile expressed by human dendritic cells is dependent on cell subtype and mode of activation.

In the present study, we have analyzed the pattern of cytokines expressed by two independent dendritic cell (DC) subpopulations generated in vitro from human cord blood CD34+ progenitors cultured with granulocyte-macrophage CSF and TNF-alpha. Molecularly, we confirmed the phenotypic differences discriminating the two subsets: E-cadherin mRNA was only detected in CD1a+-derived DC, whereas CD68 and factor XIIIa mRNAs were observed exclusively in CD14+-derived DC. Semiquantitative reverse-transcriptase PCR analysis revealed that both DC subpopulations spontaneously expressed IL-1alpha, IL-1beta, IL-6, IL-7, IL-12 (p35 and p40), IL-15, IL-18, TNF-alpha, TGF-beta, macrophage CSF, and granulocyte-macrophage CSF, but not IL-2, IL-3, IL-4, IL-5, IL-9, and IFN-gamma transcripts. Both subpopulations were shown to secrete IL-12 after CD40 triggering. Interestingly, only the CD14+-derived DC secreted IL-10 after CD40 activation, strengthening the notion that the two DC subpopulations indeed represent two independent pathways of DC development. Furthermore, both DC subpopulations expressed IL-13 mRNA and protein following activation with PMA-ionomycin, but not with CD40 ligand, in contrast to IL-12 and IL-10, revealing the existence of different pathways for DC activation. Finally, we confirmed the expression of IL-7, IL-10, and IL-13 mRNA by CD4+ CD11c+ CD3- DC isolated ex vivo from tonsillar germinal centers. Thus, CD14+-derived DC expressing IL-10 and factor XIIIa seemed more closely related to germinal center dendritic cellsGCDC than to Langerhans cells.

Antigens, CD1↗

PubMed1998

Somatic hypermutation introduces insertions and deletions into immunoglobulin V genes.

During a germinal center reaction, random mutations are introduced into immunoglobulin V genes to increase the affinity of antibody molecules and to further diversify the B cell repertoire. Antigen-directed selection of B cell clones that generate high affinity surface Ig results in the affinity maturation of the antibody response. The mutations of Ig genes are typically basepair substitutions, although DNA insertions and deletions have been reported to occur at a low frequency. In this study, we describe five insertion and four deletion events in otherwise somatically mutated VH gene cDNA molecules. Two of these insertions and all four deletions were obtained through the sequencing of 395 cDNA clones (approximately 110,000 nucleotides) from CD38+IgD- germinal center, and CD38-IgD- memory B cell populations from a single human tonsil. No germline genes that could have encoded these six cDNA clones were found after an extensive characterization of the genomic VH4 repertoire of the tonsil donor. These six insertions or deletions and three additional insertion events isolated from other sources occurred as triplets or multiples thereof, leaving the transcripts in frame. Additionally, 8 of 9 of these events occurred in the CDR1 or CDR2, following a pattern consistent with selection, and making it unlikely that these events were artifacts of the experimental system. The lack of similar instances in unmutated IgD+CD38- follicular mantle cDNA clones statistically associates these events to the somatic hypermutation process (P = 0.014). Close scrutiny of the 9 insertion/deletion events reported here, and of 25 additional insertions or deletions collected from the literature, suggest that secondary structural elements in the DNA sequences capable of producing loop intermediates may be a prerequisite in most instances. Furthermore, these events most frequently involve sequence motifs resembling known intrinsic hotspots of somatic hypermutation. These insertion/deletion events are consistent with models of somatic hypermutation involving an unstable polymerase enzyme complex lacking proofreading capabilities, and suggest a downregulation or alteration of DNA repair at the V locus during the hypermutation process.

Amino Acid Sequence↗

PubMed1998

CD40L activation of dendritic cells down-regulates DORA, a novel member of the immunoglobulin superfamily.

Using a cDNA subtraction technique, a novel member of the immunoglobulin superfamily was isolated from human Dendritic cells (DC). This cDNA which we named DORA, for DOwn-Regulated by Activation encodes a protein belonging to the CD8 family of receptors containing a single V type loop domain with an associated J chain region, a transmembrane region containing an atypical tyrosine residue and a cytoplasmic domain containing three putative tyrosine phosphorylation sites. The hDORA gene has been localised to chromosome 16. From database searches a rat cDNA was identified that encoded a polypeptide with 63% identity to hDORA. The expression of the human cDNA was studied in detail. Northern blot analysis revealed 1.0 kb and 2.5 kb mRNAs in peripheral blood lymphocytes, spleen and lymph node, while low levels were observed in thymus, appendix, bone marrow and fetal liver. No signal was noted in non-immune system tissues. By RT-PCR analysis of hDORA revealed expression in cells committed to the myeloid lineage but not in CD34+ precursors or B cells and low expression in T cells. Expression was also observed in DC, purified ex vivo or generated in vitro from either monocytes or CD34+ progenitors. This was down-regulated following activation both by PMA and Ionomycin treatment and also by CD40L engagement. In situ hybridisation performed on tonsil sections showed the presence of hDORA in cells within Germinal Centers. This structure and expression suggests a function as a co-receptor, perhaps in an antigen uptake complex, or in homing or recirculation of DC.

Amino Acid Sequence↗

PubMed1998

A novel lysosome-associated membrane glycoprotein, DC-LAMP, induced upon DC maturation, is transiently expressed in MHC class II compartment.

We have identified a novel lysosome-associated membrane glycoprotein localized on chromosome 3q26.3-q27, DC-LAMP, which is homologous to CD68. DC-LAMP mRNA is present only in lymphoid organs and DC. A specific MAb detects the protein exclusively in interdigitating dendritic cells. Expression of DC-LAMP increases progressively during in vitro DC differentiation, but sharply upon activation with LPS, TNFalpha, or CD40L. Confocal microscopy confirmed the lysosomal distribution of the protein. Furthermore, DC-LAMP was found in the MHC class II compartment immediately before the translocation of MHC class II molecules to the cell surface, after which it concentrates into perinuclear lysosomes. This suggests that DC-LAMP might change the lysosome function after the transfer of peptide-MHC class II molecules to the surface of DC.

Amino Acid Sequence↗

PubMed1998

Dendritic cells enhance the differentiation of naïve B cells into plasma cells in vitro.

We have shown previously that in vitro-generated human dendritic cells have an effect on the response of B cells at various stages of their differentiation. In a culture system described for the in vitro induction of plasma-cell differentiation, it was reported that naïve B cells have a poor propensity to differentiate into plasma cells. In such a culture system, 12% of naïve B cells differentiated into plasma cells in the presence of IL-2 and IL-10, despite the interruption of CD40 signalling which is necessary for plasma-cell differentiation. However, as reported herein, naïve B cells differentiated fully into plasma cells in response to dendritic cells. Addition of dendritic cells enhanced this differentiation strikingly by recruiting 57% of B cells as plasma cells producing IgM, but also IgG and IgA. In this model, dendritic cells act in synergy with IL-2 at an early stage of CD40-dependent B-cell differentiation, while IL-2 and IL-10 act together, at a later stage, in the generation of plasma cells in a CD40-independent manner. Thus, in addition to the key role played by dendritic cells in the initiation of T-cell responses, our results suggest that dendritic cells regulate humoral responses.

B-Lymphocytes↗

PubMed1998

Amino acid insertions and deletions contribute to diversify the human Ig repertoire.

The sequence analysis of Ig variable region genes transcribed within different B-cell subpopulations from human tonsil led us to identify a rare DNA sequence modification event consisting of bp insertions and/or deletions (I/D). Although these events were previously reported, they had never been formally associated with the somatic hypermutation process. I/D events share with more conventional somatic hypermutation events their localization within hypervariable regions and, most particularly, within DNA motifs known to be mutational hot spots. Repetitive DNA tracts or DNA elements capable of forming DNA loop intermediates seem to be the preferred substrate for I/D to occur. These characteristics suggest a model for somatic hypermutation reminiscent of the "polymerase slippage" model involved in replication and repair mutations in prokaryotes, yeast, and mammals.

Amino Acid Substitution↗

PubMed1998

The interleukin-17 gene of herpesvirus saimiri.

In comparison to wild-type herpesvirus saimiri, viral interleukin-17 gene knockout mutants have unaltered behavior regarding viral replication, T-cell transformation in vitro, and pathogenicity in cottontop tamarins. Thus, this gene is not required for T-cell lymphoma induction but may contribute to apathogenic viral persistence in the natural host, the squirrel monkey.

Animals↗

PubMed1998

The immunoglobulin E-allergen interaction: a target for therapy of type I allergic diseases.

The interaction of immunoglobulin E and otherwise harmless antigens (allergens) leads in sensitized individuals through effector cell activation to the immediate induction of a cascade of inflammatory reactions, the hallmark of type I allergy. Recently, the molecular and structural characterization of allergens, specific IgE antibodies and their epitopes has made rapid progress. Here we discuss active and passive strategies for therapy of type I allergy, which are based on interfering with the IgE-allergen interaction.

Allergens↗

PubMed1998

Interleukin-17 activates human renal epithelial cells in vitro and is expressed during renal allograft rejection.

Local production of cytokines plays a critical role in the regulation of pathophysiologic processes leading to rejection of transplanted organs. In the present study, the possible role of interleukin-17 (IL-17), a recently identified cytokine with unique properties, was investigated. IL-17 is specifically produced by activated T cells, whereas biological activities are restricted to the activation of nonhematopoietic cells. In vitro, IL-17 induced primary human proximal tubular epithelial cells, a type of cell regulating local interstitial inflammatory responses, to secrete higher levels of IL-6, IL-8, and monocyte chemoattractant protein-1, but not of the chemokine RANTES. The effect was specific for IL-17, because it was completely abrogated by a neutralizing anti-IL-17 antibody and was demonstrated to be dose- and time-dependent. In addition, IL-17 increased the production of complement component C3 by human proximal tubular epithelial cells, but not of other complement components. Immunofluorescence showed expression of IL-17 in kidney biopsies from patients suffering from graft rejection (8 of 8 positive), whereas pretransplant biopsies and normal kidneys were negative (0 of 6). Analysis of whole kidney isolates confirmed the presence of IL-17 mRNA by reverse transcription-PCR. IL-17 expression could also be found in in vitro cultured and activated graft-infiltrating T cells. These results represent the first demonstration of IL-17 protein expression in pathologic conditions and suggest that IL-17 might be important in the regulation of local inflammatory responses.

Base Sequence↗

PubMed1998

Interleukin-17.

The particular interest of IL-17, a homodimeric cytokine of about 32 kDa, is the strict requirement for an activation signal to induce its expression from a rather restricted set of cells, human memory T cells or mouse alpha beta TCR+CD4-CD8- thymocytes. In contrast with the tightly controlled expression pattern of this gene, the IL-17 receptor, a novel cytokine receptor, is ubiquitously distributed but apparently more abundant in spleen and kidney. In addition to its capture by the T lymphotropic Herpesvirus Saimiri (HVS), this cytokine is inducing the secretion of IL-6, IL-8, PGE2, MCP-1 and G-CSF by adherent cells like fibroblasts, keratinocytes, epithelial and endothelial cells. IL-17 is also able to induce ICAM-1 surface expression, proliferation of T cells, and growth and differentiation of CD34+ human progenitors into neutrophils when cocultured in presence of irradiated fibroblasts. In vitro, IL-17 synergizes with other proinflammatory signals like TNF alpha for GM-CSF induction, and with CD40-ligand for IL-6, IL-8, RANTES and MCP-1 secretion from kidney epithelial cells. In vivo, injection of IL-17 induces a neutrophilia, except in IL-6-KO mice. The involvement of IL-17 in rejection of kidney graft has also been demonstrated. The role of this T cell secreted factor in various inflammatory processes is presently investigated.

Animals↗

PubMed1998

Interleukin-4 and interleukin-13: their similarities and discrepancies.

Interleukin-4 (IL-4) and the closely related cytokine, interleukin-13 (IL-13) share many biological and immunoregulatory functions on B lymphocytes, monocytes, dendritic cells and fibroblasts. Both IL-4 and IL-13 genes are located in the same vicinity on chromosome 5 and display identical major regulatory sequences in their respective promoters, thus explaining their restricted secretion pattern to activated T cells and mast cells. The IL-4 and IL-13 receptors are multimeric and share at least one common chain called IL-4R alpha. Recent progress made in the description of IL-4 and IL-13 receptor complex have demonstrated the existence of two types of IL-4 receptors: one constituted by the IL-4R alpha and the gamma c chain, and a second constituted by the IL-4 R alpha and the IL-13R alpha 1 and able to transduce both IL-4 and IL-13 signals. Specific IL-13 receptors are results from the association between the IL-4R alpha and the IL-13R alpha 2 or between two IL-13R alpha. Furthermore, similarities in IL-4 and IL-13 signal transduction have been also described, thus explaining the striking overlapping of IL-4- and IL-13-induced biological activities such as regulation of antibody production and inflammation. However, the restricted expression of IL-4 to type 2 helper T lymphocytes as well as the inability of IL-13 to regulate T cell differentiation due to a lack of IL-13 receptors on T lymphocytes represent the major differences between these cytokines. This would indicate that although IL-4 and IL-13 share a large number of properties, precise mechanisms of regulation are also present to guarantee their distinct functions.

Animals↗

PubMed1997

CD40 ligand stimulates proinflammatory cytokine production by human endothelial cells.

Functional expression of CD40 has recently been described on the surface of HUVEC, and activation of these cells with CD40 ligand (CD40-L) leads to increased adhesion molecule expression. Here, we analyzed the effect of CD40 triggering on cytokine production by HUVEC. CD40-L-transfected fibroblasts, in contrast to their untransfected counterparts, as well as a soluble recombinant human CD40-L/murine CD8alpha chimeric molecule were able to importantly increase (by a mean of fourfold) the production of leukemia inhibitory factor (LIF) by HUVEC. CD40-L displayed an additive effect with IL-4, IL-1alpha, and TNF-alpha on the enhancement of LIF secretion. Cyclosporin A did not affect LIF synthesis by resting or CD40-L-activated HUVEC, whereas dexamethasone diminished the basal level of LIF production and abrogated the CD40-L effect. The secretions of two other proinflammatory cytokines, granulocyte-macrophage CSF and IL-6, were also increased in the presence of CD40-L. However, CD40-L neither affected HUVEC proliferation nor rescued them from IFN-gamma- and TNF-alpha induced apoptosis. Together, these results indicate that endothelial cell activation by CD40-L may play an important role not only in leukocyte recruitment through enhancement of adhesion molecule expression, but also in the maintenance of an inflammatory loop through the increase in proinflammatory cytokine secretion.

Apoptosis↗

PubMed1997

Fas-independent apoptosis of activated T cells induced by antibodies to the HLA class I alpha1 domain.

In addition to their major function in antigen presentation and natural killer cell activity regulation, HLA class I molecules may modulate T-cell activation and proliferation. Monoclonal antibodies (MoAbs) that recognize distinct epitopes of HLA class I molecules were reported to interfere with T-cell proliferation. We show here that two MoAbs (mouse MoAb90 and rat YTH862) that bind to an epitope of the alpha1 domain of HLA class I heavy chain induce apoptotic cell death of activated, but not resting, peripheral T lymphocytes. Other reference anti-HLA class I antibodies specific for distinct epitopes of the alpha1 (B9.12.1), alpha2 (W6/32), or alpha3 (TP25.99) domains of the heavy chain decreased T-cell proliferation but had little or no apoptotic effect. Apoptosis shown by DNA fragmentation, phosphatidylserine externalization, and decrease of mitochondrial transmembrane potential was observed whatever the type of T-cell activator. Apoptosis did not result from Fas/Fas-L interaction and distinct though partly overlapping populations of activated T cells were susceptible to Fas- and HLA class I-mediated apoptosis, respectively. Induction of apoptosis did not require HLA class I cross-linking inasmuch as it could be observed with monovalent Fab' fragments. The data indicate that MoAb90 and YTH862 directed against the alpha1 domain of HLA class I trigger apoptosis of activated T lymphocytes by a pathway which does not involve Fas-ligand.

Animals↗

PubMed1997

In vitro triggering of somatic mutation in human naive B cells.

During T cell-dependent immune response, germinal center B cells accumulate somatic mutations in their Ig V(D)J genes and give rise to affinity-selected B cells. We tested several culture conditions for triggering somatic mutation in human tonsillar naive slgD+CD23+ cells after cross-linking their membrane Igs. CD40 activation, in the presence of exogenous cytokines (IL-2, IL-4, and IL-10), induced proliferation and isotype switch without somatic mutation. In contrast, after coculture with anti-CD3-activated cloned T cells, somatic mutation accumulated in a fraction of naive B cells. Mutations included shared as well as independent events in clonally related sequences, allowing reconstitution of genealogic trees generated in vitro. Naive tonsillar B cells sorted for slgD expression can be induced to mutate their Ig V(H) gene upon coculture with activated T cells, thereby providing a model to study somatic hypermutation in vitro.

Amino Acid Sequence↗

PubMed1997

Measles virus infects human dendritic cells and blocks their allostimulatory properties for CD4+ T cells.

Measles causes a profound immune suppression which is responsible for the high morbidity and mortality induced by secondary infections. Dendritic cells (DC) are professional antigen-presenting cells required for initiation of primary immune responses. To determine whether infection of DC by measles virus (MV) may play a role in virus-induced suppression of cell-mediated immunity, we examined the ability of CD1a+ DC derived from cord blood CD34+ progenitors and Langerhans cells isolated from human epidermis to support MV replication. Here we show that both cultured CD1a+ DC and epidermal Langerhans cells can be infected in vitro by both vaccine and wild type strains of MV. DC infection with MV resulted within 24-48 h in cell-cell fusion, cell surface expression of hemagglutinin, and virus budding associated with production of infectious virus. MV infection of DC completely abrogated the ability of the cells to stimulate the proliferation of naive allogeneic CD4+ T cell as early as day 2 of mixed leukocyte reaction (MLR) (i.e., on day 4 of DC infection). Mannose receptor-mediated endocytosis and viability studies indicated that the loss of DC stimulatory function could not be attributed to the death or apoptosis of DC. This total loss of DC stimulatory function required viral replication in the DC since ultraviolet (UV)-inactivated MV or UV-treated supernatant from MV-infected DC did not alter the allostimulatory capacity of DC. As few as 10 MV- infected DC could block the stimulatory function of 10(4) uninfected DC. More importantly, MV-infected DC, in which production of infectious virus was blocked by UV treatment or paraformaldehyde fixation, actively suppressed allogeneic MLR upon transfer to uninfected DC-T-cultures. Thus, the mechanisms which contribute to the loss of the allostimulatory function of DC include both virus release and active suppression mediated by MV-infected DC, independent of virus production. These data suggest that carriage of MV by DC may facilitate virus spreading to secondary lymphoid organs and that MV replication in DC may play a central role in the general immune suppression observed during measles.

CD4-Positive T-Lymphocytes↗