Search PubMed⌕ Search

Biomedical subjects

M C Maillot

Publications and source records attributed to M C Maillot.

At least 19 recordsLinked to original sources
PubMed1999

Prevention of autoimmune attack by targeting specific T-cell receptors in a severe combined immunodeficiency mouse model of myasthenia gravis.

Myasthenia gravis (MG) is an autoimmune disease targeting the skeletal muscle acetylcholine receptor. We have previously demonstrated a selection bias of CD4+ T cells expressing the Vbeta5.1 T-cell receptor gene in the thymus of HLA-DR3 patients with MG. To evaluate the pathogenicity of these cells, severe combined immunodeficiency mice engrafted with MG thymic lymphocytes were treated with anti-Vbeta5.1 antibody. Signs of pathogenicity (eg, acetylcholine receptor loss and complement deposits at the muscle end plates of chimeric mice) were prevented in anti-Vbeta5.1-treated severe combined immunodeficiency chimeras. Pathogenicity was mediated by autoantibodies against acetylcholine receptor. Thymic cells depleted of Vbeta5.1-positive cells in vitro before cell transfer were nonpathogenic, indicating that Vbeta5.1-positive cells are involved in the production of pathogenic autoantibodies. Acetylcholine receptor loss was prevented by Vbeta5.1 targeting in HLA-DR3 patients only, demonstrating specificity for HLA-DR3-peptide complexes. The action of the anti-Vbeta5.1 antibody involved both the in vivo depletion of Vbeta5.1-expressing cells and an increase in the interferon-gamma/interleukin-4 ratio, pointing to an immune deviation-based mechanism. This demonstration that a selective and specific T-helper cell population is involved in controlling pathogenic autoantibodies in MG holds promise for the treatment of MG.

Adolescent↗
PubMed1997

Production and roles of IL-6, IL-10, and IL-13 in B-lymphocyte malignancies and in B-lymphocyte hyperactivity of HIV infection and autoimmunity.

We analyzed the production and the roles of IL-6, IL-10, and IL-13 in B-lymphoid malignancies and in specific diseases with B-lymphocyte hyperactivity. Both IL-13 and IL-10 genes are expressed in B-cell lymphomas. However, their contribution to tumor progression is unclear. In certain lymphoproliferative disorders that develop in transplanted patients, IL-6 is produced by malignant cells and is a major factor of their proliferation. In other lymphomas, the IL-6 gene is expressed only in malignancies where differentiated malignant cells are present. In these lymphomas, IL-6 is produced by stromal cells, and the malignant cells express the IL-6 receptor. In patients with HIV infection, the level of production of IL-6, IL-10, and IL-13 is not higher than those of other conditions with immune activation. However, IL-6 contributes to increased production of IgG and IgA in vivo. In Castleman's disease, IL-6 is produced in the lymph node germinal centers, partly originating from follicular dendritic cells, which may explain some of the pathogenesis of this disease. In systemic lupus erythematosus, the critical cytokine is IL-10, which is produced in large amounts by B lymphocytes and monocytes and is responsible for autoantibody production. Taken together, these data emphasize the roles of IL-6 and IL-10, usually produced by nonlymphoid cells, on B lymphocytes, either malignant or hyperactivated.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Antagonistic effect of interferon-gamma on tat-induced transactivation of HIV long terminal repeat.

Interferon-gamma (IFN-gamma) has been shown to inhibit human immunodeficiency virus (HIV) replication in macrophages. However, the site of its effect on the HIV infectious cycle is unknown. We show here that IFN-gamma inhibits the transactivation of HIV long terminal repeat (LTR) during viral infection and that it antagonizes tat effect in HT4LacZ-1 cells. HT4LacZ-1 is an indicator CD4+ HeLa cell line for HIV infectivity, because it harbors a HIV LTR-LacZ gene susceptible to transactivation by tat. It was used in combination with a computer-assisted image analyzer to quantify: (i) the number of transactivated foci following HIV infection, (ii) their individual level of transactivation, and (iii) the fusion potency of infected cells. IFN-gamma induced a 75% decrease of the number of transactivated foci following infection of HT4LacZ-1 cells by HIV. The remaining 25% foci still susceptible to transactivation were transactivated at a lower level than in control cultures, and the fusion potency of infected cells was strongly decreased. IFN-gamma acted after HIV entry into the cell and independently of reverse transcription. IFN-gamma antagonized tat-induced LTR transactivation: it inhibited transactivation of HT4LacZ-1 cells when tat was provided either from a SV40-based expression vector of tat or by polyethylene glycol-induced cell fusion with HeLa-tat-III cells. These results suggest that IFN-gamma affects the expression or the activity of cellular factors interacting with tat and that the high level of IFN-gamma production associated with HIV infection plays a role in the establishment of HIV latency.

Genes, tat↗
PubMed1991

Activation of cytotoxic cells in hyperplastic lymph nodes from HIV-infected patients.

Serine esterase B (SE B) is a protein contained in cytoplasmic granules of cytotoxic T lymphocytes and natural killer cells; SE B gene is transcribed upon activation of these cytotoxic cells. In order to show the in vivo interactions between HIV-infected cells and anti-HIV cytotoxic cells we analysed, by in situ hybridization, the expression of the SE B gene in eight hyperplastic lymph nodes from HIV-1-infected patients presenting with persistent generalized lymphadenopathy. We detected numerous cells expressing the SE B gene. The mean number of positive cells was 3.2 times higher in HIV lymph nodes than in six non-HIV hyperplastic lymph nodes studied in parallel (P less than 0.05). In control lymph nodes, the SE B gene was expressed only in interfollicular areas; virtually no cells expressed the SE B gene within follicles. In contrast, in HIV lymph nodes cells expressing the SE B gene were distributed either in interfollicular areas or within follicles. Expression of the SE B gene inside follicles was thus a specific feature of HIV lymph nodes (P less than 0.001) and was associated with the presence of HIV antigens and RNA at the same site. These results suggest that cytotoxic cells are activated in follicles of HIV lymph nodes and may be involved in the lysis of HIV-infected cells. Such a phenomenon may explain the development of follicle lysis, a specific feature of HIV lymph nodes. It may also inhibit the spreading of HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Production of interleukins in human immunodeficiency virus-1-replicating lymph nodes.

To document the in vivo interactions occurring between the immune system and HIV replicating cells, we analyzed using in situ hybridization the production of IL-1 beta, IL-6, IL-2, and INF-gamma in eight hyperplastic lymph nodes from HIV-1 infected patients. Numerous IL-1 beta- and IL-6-producing cells associated in clusters were detected in sinuses. Few individual IL-1 beta- and IL-6-producing cells were present in interfollicular and follicular areas. IL-2- and INF-gamma-producing cells were observed in all lymph node compartments, with a selective enrichment in germinal centers. The amount and distribution of IL-1 beta, IL-6-, and IL-2-producing cells in HIV lymph nodes were not different from those found in six HIV unrelated hyperplastic lymph nodes. In contrast, a higher level of INF-gamma production was observed in HIV-1 lymph nodes. The CD8+ cells that accumulate in germinal centers of HIV lymph nodes (and not in non-HIV germinal centers) were actively involved in this INF-gamma production. INF-gamma synthesizing cells were in direct contact with cells containing HIV core antigens and HIV RNA. Thus a high INF-gamma production may characterize anti-HIV T cell immune response, potentially contributing to control of viral spreading as well as to the development of follicle lysis.

Adult↗
PubMed1990

Syncytium induction by fresh HIV isolates: quantitative analysis using a transactivation beta-gal assay.

We used a quantitative bioassay (the beta-gal assay) to visualize and quantify syncytium induction by fresh HIV isolates. This bioassay is based on the transactivation by tat of a chimeric gene comprising an HIV-1 long terminal repeat (LTR) fused to a modified lacZ gene of Escherichia coli. The chimeric gene encodes a beta-galactosidase which is translocated to the nucleus. It allows the enzymatic staining of all nuclei from HIV-induced syncytia. Using this unequivocal assay (the beta-gal assay), we could assess the syncytium-inducing properties of fresh HIV isolates after only 4 days of coculture of patient lymphocytes with activated normal lymphocytes. Syncytium-inducing HIV isolates were detected in 11 out of 40 seropositive patients studied. They were isolated mainly from AIDS patients: eight out of 17 grade IV (according to Centers for Disease Control criteria) patients were infected with syncytium-inducing strains. However, of 23 grade II and III patients tested, syncytium-inducing HIV strains were isolated from three cases. These three patients displayed no detectable p24 antigenaemia and had a CD4+ cell count of greater than 300 cells/microliter. The in vitro replication rate of HIV grown from 36 patient blood samples was then examined by sequential p24 antigen measurements in coculture supernatants. The 10 samples leading to syncytium formation also exhibited the highest replication rate. The possibility of unequivocally detecting syncytium-inducing strains after only a few days of coculture will make this detection routine and rapid. In addition, the limited period of amplification required is a significant advantage as it minimizes the emergence of HIV variants selected during long-term in vitro cultures.

Acquired Immunodeficiency Syndrome↗
PubMed1990

IL-2 mRNA expression in Tac-positive malignant lymphomas.

Expression of the IL-2 receptor (Tac antigen/CD25) is documented in malignant lymphomas. Because IL-2 is a major lymphocyte growth factor, an IL-2-dependent growth could be involved in the proliferation of Tac-positive lymphomas. Indeed such a mechanism has been demonstrated experimentally for the growth of T-cell lines. To investigate this point in human lymphomas, we used in situ hybridization to analyze the expression of the IL-2 gene in 20 non-Hodgkin's lymphomas, among which 12 expressed the IL-2 receptor. Nine of these were anaplastic large cell lymphomas expressing the Ki-1-related antigen. We here show that IL-2-producing cells are present in all the lymphomas we analyzed. As a mean, there is no significant difference in the percentage of IL-2-producing cells between Tac-positive and -negative lymphomas. However, the level of IL-2 production is highly heterogeneous in both groups, and the highest density of IL-2-producing cells was observed in 2 Tac-positive lymphomas. Simultaneous detection of cellular antigens and of IL-2 mRNA demonstrates that IL-2 is produced by reactive T cells rather than by tumor cells. These results suggest that if IL-2 is involved in the growth of Tac-positive lymphomas, it acts as a paracrine, rather than an autocrine, factor.

Adolescent↗
PubMed1989

Visualizing interleukin 2 gene expression at the single cell level.

To analyze the expression of the interleukin (IL)2 gene at the single cell level, we have constructed a chimeric gene in which the regulatory sequences from the mouse IL2 gene were fused 5' proximal to the coding region of the Escherichia coli beta-galactosidase (lacZ) gene. Once stably introduced into a T cell hybridoma, the IL 2-lacZ reporter gene was shown to display a pattern of induction similar to the one observed for the resident IL 2 gene. Two points emerged from monitoring IL 2 expression for the resident IL2 gene. Two points emerged from monitoring IL 2 expression at the single cell level. First, upon activation the expression of the IL2-lacZ gene appears asynchronous. Second, at the peak of induction the percentage of beta-galactosidase+ cells never reached 100% and the level of beta-galactosidase reached among positive cells was highly heterogeneous within a cloned population of T cells. In combination with the possibility to sort viable lymphocytes according to lacZ expression, the IL2-lacZ reporter gene described herein should provide a way to isolate somatic cell mutants deficient in signal transduction by the T cell antigen receptor complex.

Animals↗
PubMed1982

Differential effects of azathioprine on T cells regulating murine B-cell function.

We describe selective effects of azathioprine (Az) on T-cell subpopulations regulating the primary in vitro antibody response of mouse spleen cells to the T-independent antigen TNP-polyacrylamide. This response is susceptible to the effect of two kinds of non-specific suppressor cells: (i) spontaneously-induced suppressor, generated after 4-5 days culture in the presence of 2 micrograms/ml of concanavalin A (Con A). Indeed, both these precultured cells lead to a cell dose-dependent suppression of the anti-TNP response when transferred at the initiation of antigen-stimulated fresh cell cultures. T cells are the effectors of both these suppressions and seem to directly suppress the B-cell response. We tested the in vitro effect of Az (10(-1) micrograms/ml) on the generation of these two sets of suppressors. Whereas that of Con-A-induced suppressors proves to be resistant, that of spontaneously-induced T suppressors is totally prevented by the addition of Az in the preculture medium. Instead, Az treatment allows the manifestation of a spontaneously-induced helper T cell, simultaneously generated, which is able to increase a T-independent antibody response and quite resistant to the in vitro effect of Az. Thus, this study demonstrates that different subpopulations of T lymphocytes regulating the B-cell antibody response exhibit a selectivity to Az, implying different cell proliferation requirements and/or different cellular origin.

Acrylic Resins↗
PubMed1979

Macrophage requirement for the in vitro response to an insolubilized T-independent antigen.

The role of macrophages in the in vitro response of mouse spleen cells to the insolubilized, T-independent antigen trinitrophenylated polyacrylamide (TNP-PAA) is demonstrated by the following points. The response is abolished by filtration on Sephadex G-10 and can be restored by the addition of splenic adherent cells, deficient in either B or T cells, or by 2-mercaptoethanol (2ME). It is suppressed upon elimination of phagocytic cells by silica, and restored by 2-ME. 2-ME can restore a normal response from zero, in cultures depleted of both adherent and phagocytic cells, and is efficient in the absence of mature T cells. Experiments in microcultures show that large numbers of macrophages can stimulate a supra-optimal response from B cells. This response is only obtained in the presence of the antigen, and is specific for TNP. These results show that microphages, probably by their polyclonal B-cell activator (PBA) property, play a role in the specific response to TNP-PAA. This prompts us to discuss the respective roles in the B-cell response of this PBA activity and of the interaction of the antigen with the specific B-cell receptors.

Animals↗
PubMed1977

Enhancing effect of low dose cyclophosphamide treatment on the in vitro antibody response.

We have studied the effect of cyclophosphamide (CY) administration on the subsequent in vitro antibody response in the mouse. Treatment with a low dose (20 mg/kg) of CY four days before culture results in an increased IgM response to the T-independent antigen trinitrophenylated polyacrylamide (TNP-PAA), without affecting the background response of unstimulated cultures. This suggests that CY treatment eliminates a short-lived suppressor cell, involved in the regulation of the in vitro B cell response. In contrast, the same regimen decreases the ability of nude mouse spleen cells to respond to TNP-PAA, showing that the target of CY-enhancing effect is a mature T cell. The increased response observed in conventional mice should be the result of a balance between the direct suppressive effect of CY on B cells and the elimination of a suppresor T cell, the latter phenomenon being of predominant significance in our conditions. The target of CY-enhancing effect is nonadherent to plastic, but adherent to Sephadex G-10 columns.

Acrylamides↗
PubMedDate not supplied

Cytokines in HIV infection.

Human immunodeficiency virus infection leads to a deregulated production of a number of cytokines. Some of them (IL-1, IL-6, TNF-alpha, interferon-gamma) are produced in increased amounts in vivo, whereas the production of IL-2 is decreased. This latter abnormality plays a pivotal role in the establishment of the immunodeficiency. Some cytokines (IL-1, IL-6, TNF-alpha) stimulate the in vitro replication of HIV, whereas others (mainly the interferons) inhibit it. The effect of cytokines in vivo in the spreading of HIV remains, however, largely unknown. Cytokines may also be involved in the development of many clinical manifestations associated with HIV infection. IL-1, IL-6 and TNF-alpha may play a role in tissue damages associated with opportunistic infections, in HIV-related encephalopathy and in cachexia. Cytokines, mainly IL-6, IL-10 and IL-13, may stimulate the growth of malignant cells during Kaposi sarcoma or lymphomas. Better knowledge of the role of cytokines during HIV infection should allow new therapeutic approaches based on the use of either recombinant cytokines or specific antagonists, with the aim of limiting both HIV spreading and the clinical manifestations of this infection.

Cytokines↗
PubMedDate not supplied

Interleukin induction of non-specific suppressor cells.

We analysed the cellular and molecular signals involved in the induction of non-specific T suppressor (Ts) cells generated in mouse spleen cell suspensions after 3-4 days' culture in the absence of conventional antigen. Using an in vitro model of primary antibody response as a suppressor assay, we showed that purified T cells were unable to generate suppressive activity. This suppression was fully restored when T cells were cultured with macrophages. In this case, Ts-cell generation was markedly increased by the addition of indomethacin suggesting a negative effect of prostaglandins in this phenomenon. Macrophages could be replaced by semi-purified IL1 as well as by recombinant IL2. Thus, in conditions of severe macrophage depletion, IL1 and/or IL2 are fully capable of inducing Ts-cell generation.

Animals↗
PubMedDate not supplied

Interleukin-13 gene expression by malignant and EBV-transformed human B lymphocytes.

Expression of the IL-13 gene in malignant tissues from 26 human B-cell lymphoid malignancies was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). A positive signal was detected in 16 cases, which included high grade B lymphomas, follicular lymphomas and B-cell chronic lymphocytic leukemias. IL-13 mRNA was also detected in the 9 malignant B cell lines and in the 6 lymphoblastoid cell lines tested, as well as in freshly isolated malignant B cells from 2 patients with a Burkitt's lymphoma. Two of 8 T-cell lymphomas and 2 of 4 T-cell lines expressed the IL-13 gene. In contrast, IL-13 gene expression was not detected in any of the 5 non-lymphoid cell lines tested. No specific binding of radiolabeled IL-13 was detected on B cell lines, suggesting an absence of IL-13 receptors on such cells. This conclusion was also supported by the inability of IL-13 or anti-IL-13 antibodies to affect the growth of malignant B cells. Taken together, these results show that both malignant and EBV-transformed B lymphocytes, either freshly isolated or maintained as cell lines, express the IL-13 gene. This raises the question of the role of B lymphocyte-derived IL-13, a B lymphocyte stimulating cytokine, on the in vivo function of normal B lymphocytes as well as on the in vivo behaviour of B lymphoid malignancies.

Animals↗
PubMedDate not supplied

Spontaneous production of interleukin-10 by B lymphocytes and monocytes in systemic lupus erythematosus.

Interleukin-10 (IL-10) production by B lymphocytes has previously been demonstrated for malignant cells and for in vitro activated normal B cells. Spontaneous in vivo production of IL-10 by normal B lymphocytes has only been demonstrated in mice, in which autoreactive Ly 1 + B cells are involved. In the present study, spontaneous expression of the IL-10 gene by peripheral blood mononuclear cells was investigated in systemic lupus erythematosus (SLE), a human disease involving autoreactive B cells. Of the 47 SLE patients tested by coupled reverse transcriptase-polymerase chain reaction, 34 scored positive, contrasting with only 1 positive out of 34 normal subjects (p < 0.001). Spontaneous in vitro production of IL-10 by PBMC, determined using an ELISA assay, was 33 times higher in SLE than in controls (2623 +/- 728 pg/ml vs 79.3 +/- 34.5 pg/ml, respectively) (p < 0.001). The level of production of IL-10 in SLE was unrelated to either clinical or biological markers of disease activity. Among PBMC, monocytes and B lymphocytes both contributed to IL-10 production, whereas T cells did not. IL-10 overproduction in SLE suggests that this Th2-type interleukin plays a role in the production of autoantibodies through pathways involving both paracrine production by monocytes and autocrine IL-10 production by autoreactive B cells.

Adolescent↗