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Biomedical subjects

F Brière

Publications and source records attributed to F Brière.

At least 19 recordsLinked to original sources
PubMed1996

Somatic mutations in human Ig variable genes correlate with a partially functional CD40-ligand in the X-linked hyper-IgM syndrome.

X-linked hyper-IgM (HIGM-1) syndrome is a rare disorder resulting from mutations in the CD40-ligand (CD40L) gene. This defect is associated with normal or elevated serum levels of IgM, and with low to undetectable levels of serum IgG, IgA, and IgE. We analyzed the somatic mutation status in Ig V genes from three unrelated HIGM-1 patients by reverse-transcription PCR and sequence analysis. Two patients (B.S. and P.S.) expressed unmutated VH6 genes. In contrast, one patient (A.T.) was found to express mutated VH6 genes. Whether the presence of somatic mutations in this patient was related to a functional CD40L was assessed by deriving T cell clones from his peripheral blood cells. Upon activation, these T cell clones expressed weakly and transiently surface CD40L, and were able to induce limited isotype switch of normal native B cells, indicating residual CD40L function. Altogether, our results 1) confirm the central role played by CD40L in the generation of somatic mutation (patients B.S. and P.S.), 2) provide an unusual illustration of the relative dissociation between somatic mutation and isotype switching (patient A.T.), and 3) demonstrate a further complexity of the X-linked HIGM syndrome that may occur despite a partially functional CD40L.

B-Lymphocytes↗
PubMed1996

Interleukin-10 induces immunoglobulin G isotype switch recombination in human CD40-activated naive B lymphocytes.

Upon activation, B lymphocytes can change the isotype of the antibody they express by immunoglobulin (Ig) isotype switch recombination. In previous studies on the regulation of human IgG expression, we demonstrated that interleukin 10 (IL-10) could stimulate IgG1 and IgG3 secretion by human CD40-activated naive (sIgD+) tonsillar B cells. To assess whether IL-10 actually promotes the DNA recombination underlying switching to these isotypes, we examined the effect of IL-10 on the generation of reciprocal products that form DNA circles as by-products of switch recombination. The content of reciprocal products characteristic of mu-gamma recombination was elevated after culture of CD40-activated tonsillar sIgD+ B cells with either IL-4 or IL-10, although high levels of IgG secretion were observed only with IL-10. Unlike IL-4, IL-10 did not induce reciprocal products of mu-epsilon and gamma-epsilon switch recombination. These results demonstrate that IL-10 promotes both switching to gamma and IgG secretion.

Antigens, CD↗
PubMed1996

Normal human IgD+IgM- germinal center B cells can express up to 80 mutations in the variable region of their IgD transcripts.

Somatic hypermutation in immunoglobulin variable region genes occurs within germinal centers. Here, we describe a subset of germinal center dark zone centroblasts that express only sIgD and have accumulated up to 80 mutations per heavy chain variable region (IgVH delta gene). Over half of the hypermutated IgVH delta sequences were found to be clonally related. This level of mutation is not observed in either IgVH gamma transcripts from the same sample or IgVH delta transcripts from peripheral blood, suggesting that these cells neither undergo isotype switch nor mature into circulating memory B cells. Optimal growth of these cells in vitro depends on CD40 ligand, T cell cytokines, and a fibroblast stroma, a combination possibly mimicking the dark zone microenvironment. Our hypothesis is that these cells may be sequestered within germinal centers, where their somatic mutation machinery is triggered. The isolation of these hypermutated B cells may represent a critical step for studying both the biology and biochemistry of somatic hypermutation.

ADP-ribosyl Cyclase↗
PubMed1996

Delayed IgG2 humoral response in infants is not due to intrinsic T or B cell defects.

The physiologically low or absent IgG2 responses of infants have been attributed to T or B cell functional immaturity. We have analyzed the capacity of adult and neonatal T lymphocytes to secrete IgG2 switch factor (IgG2-SF) and the capacity of neonatal B cells to respond to such factors. The IgG2-SF capacity was assessed on CD40-activated naive B cells, measuring IgG2 by ELISA in supernatants of cultures performed in the presence of IL-10. T cells secreted IgG2-SF together with IL-2 and IFN-gamma, after activation with a combination of anti-CD2, anti-CD28 and phorbol myristate acetate (Th1-like activation). In contrast, activation with anti-CD3 and anti-CD28, which yielded IL-4 and IL-10 but neither IL-2 nor IFN-gamma (Th2-like activation), did not result in the secretion of IgG2-SF. The supernatant of activated neonatal T cells contained IgG2-SF. Neonates' B cells produced almost as much IgG2 as did naive adult B cells. The effect of IgG2-SF was further demonstrated by its ability to induce 3-15% of CD40-activated naive B cells to express cytoplasmic IgG2 regardless of the presence of IL-10. This study demonstrates that: (i) IgG2 switch can be T cell dependent in humans, (ii) IgG2-SF is produced with Th1-like cytokines and (iii) low IgG2 responses in infants do not result from either an inability of T cells to produce IgG2-SF or an inability of B cells to undergo IgG2 switch in vitro.

Adult↗
PubMed1996

[B lymphocytes of patients with complete IgA deficiency secrete IgA in response to interleukin 10].

We have previously shown that human B lymphocytes cultured in the CD40 system, composed of an anti-CD40 mAb presented by a CD32-transfected fibroblastic cell line, proliferate but do not secrete immunoglobulins (Igs). However, the addition of particles of Staphylococcus aureus Cowan (SAC) induces B cell to secrete considerable amounts of Igs even in the absence of exogenous cytokines (CD40/SAC system). Additionally, B lymphocytes cultured in the CD40 system in the presence of human IL-10, produce high level of IgM, IgG and IgA, which are further increased by addition of SAC. Here, we have studied the capacity of peripheral blood lymphocytes from patients with IgA deficiency (IgA-D) to secrete Igs, particularly IgA after CD40 triggering. Peripheral blood mononuclear cells (PBMNC) from IgA-D patients cultured in the CD40/SAC system produced IgM and IgG, but no IgA. The addition of IL-10 to the cultures, enhanced the production of IgM and IgG and most strikingly induced the production of high amounts of IgA. The addition of IL-10 to PBMNC from IgA-D patients activated through CD40 alone resulted in the production of IgA. Thus, IL-10 can remove the block in B cell differentiation and allows B cells from IgA-D patients to differentiate into IgA secreting cells.

Adult↗
PubMed1995

Generation of memory B cells and plasma cells in vitro.

After germinal center B cells undergo somatic mutation and antigen selection, they become either memory B cells or plasma cells, but the signal requirements that control entry into either pathway have been unclear. When purified human germinal center cells were cultured with interleukin-2, interleukin-10, and cells expressing CD40 ligand, cells with characteristics of memory B cells were generated. Removal of CD40 ligand from the system resulted in terminal differentiation of germinal center B cells into cells with the characteristics of plasma cells. These results indicate that CD40 ligand directs the differentiation of germinal center B cells toward memory B cells rather than toward plasma cells.

ADP-ribosyl Cyclase↗
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

Human interleukin 10 induces naive surface immunoglobulin D+ (sIgD+) B cells to secrete IgG1 and IgG3.

During antigen-induced immune responses, human B cells switch isotype from immunoglobulin M (IgM)-IgD to IgG1-4, IgA1-2, or IgE. In the human, no cytokines have yet been demonstrated to act as switch factors for IgG1, IgG2, and IgG3. In this paper, we report that in response to interleukin 10 (IL-10), anti-CD40 activated tonsillar surface IgD+ (sIgD+) B cells are induced to secrete large amounts of IgM, IgG1, and IgG3 but neither IgG2 nor IgG4. Cord blood purified B cells and lymphocytes from Hyper-IgM patients also produced IgG1 and IgG3 after culture with anti-CD40 and IL-10. In contrast, sIgD- isotype-committed B cells produce IgG1, IgG2, and IgG3 when activated through CD40 in the presence of IL-10. Thus, in addition to its growth-promoting and differentiating activities on human B cells, IL-10 may represent a switch factor for IgG1 and IgG3.

B-Lymphocytes↗
PubMed1994

Molecular control of B lymphocyte growth and differentiation.

During antigen driven immune responses, antigen-specific naive B lymphocytes undergo a cascade of events including activation, expansion, mutations, isotype switch, selections and differentiation into either antibody secreting plasma cells or memory B cells. These antigen-dependent events, which we propose to call immunopoiesis, occur in different areas of secondary lymphoid organs, as well as other nonlymphoid organs. B cells interact with antigens and numerous cell types (T cells, dendritic cells, follicular dendritic cells and macrophages) through numerous cell surface molecules and cytokines. B cells costimulated through their antigen receptor and cytokines such as interleukin 2 (IL-2), IL-4 and IL-10 undergo limited proliferation and differentiation into immunoglobulin (Ig) secreting cells. In contrast, crosslinking of the B cell CD40 antigen, a member of the tumor necrosis factor (TNF) receptor family, results in major cellular activation further modulated by cytokines. In particular, IL-4 and IL-13 permit establishment of long-term factor-dependent B cell lines, as well as isotype switch towards the production of IgE and IgG4. Addition of IL-10 to CD40-activated B cells results in limited proliferation and remarkable differentiation into plasma cells. IL-10 also participates in isotype switch towards IgG1, IgG3 and IgA. The ligand for CD40, a member of the TNF family, is transiently expressed on activated T cells, and interrupted CD40/CD40-L interactions result in profoundly altered humoral immune responses.

Animals↗
PubMed1994

The CD40 antigen and its ligand.

CD40 is an integral membrane protein found on the surface of B lymphocytes, dendritic cells, follicular dendritic cells, hematopoietic progenitor cells, epithelial cells, and carcinomas. It is a 45-50 kDa glycoprotein of 277 aa, which is a member of the tumor necrosis factor receptor superfamily. The CD40 gene maps to human chromosome 20q11-2-q13-2. CD40 binds to a ligand (CD40-L) which is an approximately 35 kDa glycoprotein of 261 aa, a member of the tumor necrosis factor superfamily. The CD40-L gene maps to human chromosome Xq24. This CD40-L is expressed on activated T cells, mostly CD4+ but also some CD8+ as well as basophils/mast cells. The CD40-L is defective in the X-linked hyper-IgM syndrome. Cross-linking of CD40 with immobilized anti-CD40 or cells expressing CD40-L induces B cells to proliferate strongly, and addition of IL-4 or IL-13 allows the generation of factor-dependent long-term normal human B cell lines and the secretion of IgE following isotype switching. Addition of IL-10 results in very high immunoglobulin production with limited cell proliferation. IL-10 induces naive B cells to produce IgG3, IgG1, and IgA1, and further addition of TGF beta permits the secretion of IgA2. Several evidences suggest that CD40-dependent activation of B cells is important for the generation of memory B cells within the germinal centers: (i) CD40 activated germinal center B cells cultured in the presence of IL-4 acquire a memory B cell phenotype, (ii) CD40 activated B cells can undergo isotype switching, (iii) the deficit of CD40-L results in the hyper-IgM syndrome characterized by lack of germinal centers in secondary lymphoid organ follicles and lack of IgG, IgA, and IgE, and (iv) CD40-L positive T cells are present in secondary follicles. Thymic epithelial cells, activated monocytes, and dendritic cells express CD40 antigen which may be involved in an enhanced cytokine production by these cells, allowing an amplification of T cell proliferation. Finally, as other members of the tumor necrosis factor receptor family have been shown to bind several ligands, it is possible that CD40 may bind other ligands that may trigger CD40 on different cell types such as hematopoietic cells or epithelial cells.

Amino Acid Sequence↗
PubMed1994

Interleukin 10 induces B lymphocytes from IgA-deficient patients to secrete IgA.

We have previously shown that human B lymphocytes cultured in the CD40 system, composed of an anti-CD40 mAb presented by a CD32-transfected fibroblastic cell line, proliferate but do not secrete antibodies. However, the addition of particles of Staphylococcus aureus Cowan (SAC) induces B cell differentiation even in the absence of exogenous cytokines (CD40/SAC system). Additionally, B lymphocytes cultured in the CD40 system in the presence of human IL-10, produce IgM, IgG, and IgA, and Ig levels are further increased by SAC. Here, we have studied the capacity of peripheral blood lymphocytes from patients with IgA deficiency (IgA-D) to secrete Igs, particularly IgA after CD40 triggering. Peripheral blood mononuclear cells (PBMNC) from IgA-D patients cultured in the CD40/SAC system produced IgM and IgG, but not IgA. The addition of IL-10 to the cultures, enhanced the production of IgM and IgG and most strikingly induced the production of high amounts of IgA. The addition of IL-10 to PBMNC from IgA-D patients activated through CD40 alone resulted in the production of IgA. Thus, SAC and anti-CD40 mAb stimulate B cells to differentiate into cells secreting IgG and IgM whereas IL-10 plays a central role in inducing B cells from IgA-D patients to differentiate into IgA secreting cells.

Adolescent↗
PubMed1994

[Reconstitution of immunoglobulin production in patients with variable immunodeficiency syndrome (CVI) by the CD40 system and IL-10].

Common variable immunodeficiency (CVI) is widely believed to involve a primary B cell defect, however, there is increasing evidence of T cell dysfunction in these patients. To test the hypothesis that B cells of patients with CVI are not defective, we investigated whether immunoglobulin production can be induced by activation through the CD40 system. Our results show that 6 of 7 children with CVI produced IgG when B cells were activated through CD40 plus IL-10. In most patients, IgM and IgA production were also induced. However, we could demonstrate that failure of immunoglobulin production was not due to a defective CD40 ligand expression on T cells. Taken together, our data show that B cells of patients with CVI are functionally normal when activated through CD40 plus IL-10. IL-10 seems to be more effective than IL-2 in restoration of immunoglobulin production in such patients.

Adolescent↗
PubMed1994

IL-13 has only a subset of IL-4-like activities on B chronic lymphocytic leukaemia cells.

The recently described interleukin-13 (IL-13) has been shown to share many of the effects of IL-4 on normal B cells, including growth-promoting activity and induction of CD23. In this study, we compared the effects of IL-13 and IL-4 on B chronic lymphocytic leukaemias (B-CLL) cells. After anti-CD40 activation, both IL-13 and IL-4 promoted the DNA synthesis of B-CLL cells and increased the recovery of viable cells. The time kinetics of the proliferative response of B-CLL cells to IL-13 or IL-4 were superimposable and showed the long-lasting effect of both cytokines. As on normal B cells, both IL-4 and IL-13 synergized with IL-10 to enhance B-CLL DNA synthesis. Moreover, IL-13, like IL-4, was able to increase CD23 expression on anti-CD40-activated leukaemic B cells. The CD23 up-regulation and the DNA synthesis induced by IL-13 on anti-CD40-activated B-CLL cells, were significantly reduced when B-CLL cells were cultured with anti-IL-4 receptor monoclonal antibody, suggesting a common pathway for IL-13 and IL-4 signalling. However, after cross-linking of surface IgM, IL-4 strongly inhibited the IL-2-induced DNA synthesis of B-CLL cells, whereas IL-13 did not inhibit IL-2-driven proliferation of anti-IgM-activated B-CLL cells. Furthermore, while IL-4 strongly up-regulated the expression of CD23 on anti-IgM-activated leukaemic B cells, IL-13 only marginally increased it. Finally, IL-13, in contrast to IL-4, did not prevent the entry of B-CLL cells into apoptosis. Thus IL-13 and IL-4 display comparable effects on anti-CD40-activated B-CLL cells, which are blocked by anti-IL-4 receptor (IL-4R) monoclonal antibodies. However, IL-13-dependent effects are absent or inefficient in non-activated or anti-IgM-activated B-CLL cells. This suggests that such cells may lack functional IL-13 receptors, though IL-13R and IL-4R on B-CLL cells share a common component.

Antibodies, Monoclonal↗