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T Sornasse

Publications and source records attributed to T Sornasse.

12 recordsLinked to original sources
PubMed1997

Induction of human T helper cell type 1 differentiation results in loss of IFN-gamma receptor beta-chain expression.

Differential expression of cytokine receptors accounts for an important regulatory mechanism in differentiation of Th1/Th2 subsets. Here, we report that human Th0 and Th2 clones constitutively express transcripts for the IFN-gammaR beta-chain, whereas mRNA for this signaling component of the IFN-gamma receptor is absent in Th1 clones. Activation of T cell clones, however, resulted in a transient induction or enhancement of IFN-gammaR beta-chain mRNA expression in Th1 clones and Th0/Th2 clones, respectively. IL-12-mediated Th1 cell differentiation of naive CD4+, CD45RA+ cord blood T cells, which constitutively express IFN-gammaR beta-chain mRNA, resulted in a loss of expression of this cytokine receptor chain after 6 to 12 days of culture. In contrast, Th2 populations, differentiated from CD4+, CD45RA+ cord blood T cells in the presence of IL-4, continued to express high levels of IFN-gammaR beta-chain transcripts. The loss of IFN-gammaR beta-chain expression in Th1 populations was accompanied by a failure of IFN-gamma to induce the expression of the IFN-gamma-inducible gene, IFN response factor-1, whereas IFN-gamma was effective in inducing IFN response factor-1 mRNA expression in Th0 and Th2 cells. These results indicate that down-regulation of the IFN-gammaR beta-chain correlates with impaired IFN-gamma-induced signaling in Th1 cells. Finally, Th2 populations, generated in the presence of both IL-4 and IFN-gamma, expressed levels of IFN-gammaR beta-chain transcripts similar to those produced by cells differentiated in the presence of IL-4 only, demonstrating that IFN-gamma does not modulate the expression of its receptor. Together, these data indicate that human Th0/Th2 and Th1 subsets, respectively, can be distinguished based on the expression of the IFN-gammaR beta-chain.

CD4-Positive T-Lymphocytes↗
PubMed1996

Differentiation and stability of T helper 1 and 2 cells derived from naive human neonatal CD4+ T cells, analyzed at the single-cell level.

The development of CD4+ T helper (Th) type 1 and 2 cells is essential for the eradication of pathogens, but can also be responsible for various pathological disorders. Therefore, modulation of Th cell differentiation may have clinical utility in the treatment of human disease. Here, we show that interleukin (IL) 12 and IL-4 directly induce human neonatal CD4- T cells, activated via CD3 and CD28, to differentiate into Th1 and Th2 subsets. In contrast, IL-13, which shares many biological activities with IL-4, failed to induce T cell differentiation, consistent with the observation that human T cells do not express IL-13 receptors. Both the IL-12-induced Th1 subset and the IL-4-induced Th2 subset produce large quantities of IL-10, confirming that human IL-10 is not a typical human Th2 cytokine. Interestingly, IL-4-driven Th2 cell differentiation was completely prevented by an IL-4 mutant protein (IL-4.Y124D), indicating that this molecule acts as a strong IL-4 receptor antagonist. Analysis of single T cells producing interferon gamma or IL-4 revealed that induction of Th1 cell differentiation occurred rapidly and required only 4 d of priming of the neonatal CD4+ T cells in the presence of IL-12. The IL-12-induced Th1 cell phenotype was stable and was not significantly affected when repeatedly stimulated in the presence of recombinant IL-4. In contrast, the differentiation of Th2 cells occurred slowly and required not only 6 d of priming, but also additional restimulation of the primed CD4+ T cells in the presence of IL-4. Moreover, IL-4-induced Th2 cell phenotypes were not stable and could rapidly be reverted into a population predominantly containing Th0 and Th1 cells, after a single restimulation in the presence of IL-12. The observed differences in stability of IL-12- and IL-4-induced human Th1 and Th2 subsets, respectively, may have implications for cytokine-based therapies of chronic disease.

CD4-Positive T-Lymphocytes↗
PubMed1995

Glucocorticoids down-regulate dendritic cell function in vitro and in vivo.

Exogenous glucocorticoid hormones are widely used as therapeutical agents, whereas endogenous glucocorticoids may act as physiological immunosuppressants involved in the control of immune and inflammatory responses. The optimal activation of T lymphocytes requires two distinct signals: the major histocompatibility complex-restricted presentation of the antigen and an additional co-stimulatory signal provided by the antigen-presenting cells. There is ample evidence that, among the cells able to present the antigen, the dendritic cells (DC) have the unique property to activate antigen-specific, naive T cells in vitro and in vivo, and are therefore required for the induction of primary immune responses. In this work, we tested whether glucocorticoids affected the capacity of DC to sensitize naive T cells. Our data show that, in vitro, the steroid hormone analog dexamethasone (Dex) affects the viability of DC, selectively down-regulates the expression of co-stimulatory molecules on viable DC, and strongly reduces their immunostimulatory properties. In vivo, a single injection of Dex results in impaired antigen presenting function, a finding which correlates with reduced numbers of splenic DC. These results show that glucocorticoids regulate DC maturation and immune function in vitro and in vivo and suggest that this mechanism may play a role in preventing overstimulation of the immune system.

Animals↗
PubMed1995

Antagonizing the differentiation and functions of human T helper type 2 cells.

Allergen-specific T cells from atopic patients generally belong to the T-helper type 2 subset. IL-4 and IL-13 produced by these cells induce IgE synthesis by B cells and play a major role in allergic disease mediated by IgE. Recent advances in our understanding of the differentiation and IgE-inducing activities of T-helper type 2 cells suggest that targeting allergen-specific T cells may provide a novel way to intervene in allergy.

Animals↗
PubMed1994

Murine dendritic cells pulsed in vitro with tumor antigen induce tumor resistance in vivo.

The aim of this work is to induce tumor resistance to a B cell lymphoma in BALB/c mice using elements of the immune system. It has indeed been shown by us and by others that antigen-presenting cells (APC) like dendritic cells can induce efficient immune responses and can even substitute for Freund's adjuvant. Here we show that mice immunized with syngeneic dendritic cells pulsed in vitro with tumor antigen (BCL1 idiotype expressed by lymphoma cells) are protected against a subsequent tumor inoculation. The in vivo resistance can be correlated with the induction of a humoral response specific for the idiotype expressed by the tumor. No such protection can be achieved when B cells are used as APC. These data show that effector cells in tumor-bearing animals can be recruited and activated using dendritic cells, providing long-lasting immune surveillance.

Animals↗
PubMed1994

Immunoglobulin isotype regulation by antigen-presenting cells in vivo.

The isotype and magnitude of the B cell response clearly depends on the in vivo activation of T helper (Th) cells which secrete different lymphokines. Since Th are activated by the presentation of the antigen on specialized cells, we wished to test whether the nature of the antigen-presenting cells (APC) influences the isotypic profile of the humoral response. Data are presented showing that antigen-pulsed dendritic cells (DC) and peritoneal macrophages induce the synthesis of specific antibodies when injected in syngeneic animals. By contrast, a single injection of antigen-pulsed resting B cells does not prime the mice in vivo. Moreover, the injection of antigen-pulsed DC induces the synthesis of specific IgG2a and IgG1 antibodies, whereas peritoneal macrophages favor the production of IgG1 and IgE antibodies specific for the antigen. These data show that the isotype and the amplitude of the B cell response can be regulated by the nature of the APC, and indirectly suggest that Th cell differentiation is controlled at the level of antigen presentation.

Animals↗
PubMed1992

Antigen-pulsed dendritic cells can efficiently induce an antibody response in vivo.

The aim of this study was to develop an immunization procedure avoiding external adjuvant. Data are presented showing that syngeneic dendritic cells (DC), which have been pulsed in vitro with antigen, induce a strong antibody response in mice. By contrast, antigen (Ag)-pulsed low-density B cells, although equally able to induce interleukin 2 secretion by an Ag-specific T cell hybridoma in vitro, only weakly prime the mice in vivo. Moreover, we show that the injection of Ag-pulsed DC induces the synthesis of isotypes similar to the immunoglobulin classes detected after immunization with the same Ag in complete Freund's adjuvant. Importantly, high amounts of IgG2a antibodies are produced, suggesting that T helper type 1 cells are activated. Collectively, these data indicate that DC can initiate a primary humoral response and that they may be used as physiological adjuvant in vivo.

Animals↗
PubMed1990

Immune surveillance: both CD3+ CD4+ and CD3+ CD8+ T cells control in vivo growth of P815 mastocytoma.

The aim of this study was to examine whether a spontaneous immune response controls neoplastic growth in P815-bearing DBA/2 mice, and to characterize the cells involved in tumor resistance in vivo. Several cell lineages such as T-cell-receptor (TcR)-bearing T cells, NK cells and macrophages mediate some anti-tumor activity in vitro. P815 was chosen as a model because it is weakly immunogenic and is a good target both for tumor-specific, MHC-restricted CTL-mediated lysis and for MHC-unrestricted lysis exerted by long-term cultured lymphocytes or activated macrophages. Since most "NK-like activity" in freshly isolated populations appears to be associated with CD3- cells, whereas antigen-specific, MHC-restricted T cells mostly express CD3 determinants, CD3 was a good marker for evaluating the role of T cells and "NK" cells in tumor resistance in vivo. The survival of anti-CD3-treated animals that were inoculated with tumor cells was strongly reduced (mean survival time: 17 days vs. 40 days for the control group) and was associated with increased tumor growth rate. We followed the same approach to define the T-cell subset(s) that mediate(s) this immune response. Both CD4+ and CD8+ T cells were required for induction of immune control on neoplastic growth. The approach used has revealed the important role of CD4+ T cells in immune responses that control in vivo growth of a class-I-positive, class-II-negative tumor and suggests that these cells may play a central role in tumor resistance. Since CD4+ cells are activated by soluble, exogenous proteins, this finding may have important implications for immunotherapy.

Animals↗